Handling Control Systems Design and Function
Self-Study Program Course Number 961103
Audi of America, Inc Service Training Printed in U.S.A. Print Pr inte ed 07/ 2001 Course Co urse N umber 961 961103 103
All rights reserved. All information contained in this manual is based on the latest product information available at the time of printing. Th T he rig igh hts ar are e reserv rve ed to mak ake e chan ang ges at any time without without notice. notice. No N o part part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical or photocopying, recording or otherwise, without the prior permission of the publisher. This includes text, figures and tables. Always check Technic ical al Bull lle etin ins s an and d the Au Aud di Wo World ldw wid ide e Repair Information System for any information that may supersede any information included in this booklet.
HANDLING CONTROL SYSTEMS
ABS is the abbreviation for “anti-lock braking system.” The task of ABS is to provide the driver better braking and steering control during situations in which traction is reduced or lost. Continuing developments in passenger car ABS and traction assist systems have resulted in powerful and reliable systems that are capable of furnishing optimum braking, traction and steering response during critical conditions.
Important/Note!
New!
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HANDLING CONTROL SYSTEMS
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HANDLING CONTROL SYSTEMS Table of Contents Anti-lock Braking Systems (ABS)
Introduction Introducti on........ ................. .................. .................. .................. .................. .................. .................. ................... ................... .................. .................. ................ ................ ................. ................. ......... 1 System Syste m Abbrev Abbreviatio iations ns ......... .................. ................... ................... .................. ................... ................... .................. .................. ................... ................... ................. ................ ................ ........ 3 Introducti Intro duction on to Audi ABS System Systemss ......... ................... .................... .................... .................... .................... .................... ................... ................... ................. ................ .............. ..... 4 System Applic Application ation Chart Chart........ ................. ................. ................. ................. ................. ................. ................. .................. ................. ................. ................. ................ ............. ..... 4 Basic Operat Operation ion of ABS ......... .................. ................... ................... .................. ................... ................... ................... ................... ................... ................... ............... ............... .............. ..... 5 Commonn ABS Syste Commo System m Compon Components ents ......... ................... ................... ................... .................... ................... ................... .................... ................... ................... ................. ........... .... 6 Wheel Speed Sensors (G44, G45, G46 and G47) ................... ....................................... ......................................... ....................................... .................. 8 ABS Control Module (J104).................... (J104) ........................................ ......................................... ......................................... ........................................ ............................. ......... 10 Hydraulic Hydrau lic Unit ......... .................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. .......... 13 Brake Syste System m Warnin arningg Lights ........ ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. .............. ..... 15 Tra ct ction ion A ss ssist ist System System s
Description and Operat Description Operation ion......... .................. ................... ................... ................... ................... ................... ................... ................... ................... ................. ................. ............... ...... 17 Electronic Brake Pressure Distribution (EBD) .................... ......................................... ......................................... ........................................ .......................... ...... 17 Electronic Elect ronic Differe Differential ntial Lock (EDL) ........ ................. ................. ................. ................. ................. ................. ................. .................. ................. ................. ................. .......... 18 Anti-slip Regulation (ASR) .................. ....................................... ......................................... ........................................ ........................................ ................................. ............. 19 Electronic Elect ronic Stabi Stability lity Progr Program am (ESP (ESP)) ........ ................ ................. ................. ................. ................. ................. ................. ................. .................. ................. ................ ........ 20 AU DI A BS Systems Systems
Bosch 2S ABS ......... .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. ................ ................ .................. ........... .. 21 Bosch 5.0 ABS ......... .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. ................ ................ .................. ........... 23 Bosch 5.3 ABS ......... .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. ................ ................ .................. ........... 25 Bosch 5.7 ABS ......... .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. .................. ................ ................ .................. ........... 28 Teves MK 20 IE ABS ........ ................. .................. ................... ................... .................. .................. .................. .................. .................. .................. .................. ................ ................ ........... .. 32 Teves MK 60 ABS ......... .................. .................. .................. .................. .................. ................... ................... .................. .................. .................. .................. ............... ............... ............... ...... 34 ABS Service .................. .................................... ..................................... ..................................... ..................................... ..................................... ....................................... ............................ ....... 36 4-Level Air Suspension
Introduction Introducti on........ ................. .................. .................. .................. .................. .................. .................. ................... ................... .................. .................. ................ ................ .................. ............... ...... 37 Air Suspension Levels ................ ................................. .................................. .................................. .................................. ................................. ..................................... ........................ ... 38 Air Suspension Control Display .............. ............................. ............................... ................................ ............................... ............................... .................................. .................. 39 Manuall Suspen Manua Suspension sion Contr Control ol ......... ................... ................... ................... ................... ................... .................... ................... ................... ................... ................. ................. ............ ... 40 Conditions Condi tions for Manua Manuall Operat Operating ing Mode............. Mode...................... ................. ................. ................. ................. ................. ................. .................. ................. .......... .. 40 Service (Jack (Jack)) Mode ......... ................. ................. ................. ................. .................. ................. ................. ................. ................. ................. ................. ................. ................. ......... 41 Hoist Mode ........ ................ ................. ................. ................. ................. ................. ................. ................. .................. ................. ................. ................. ................ ................. ............... ...... 41 Automatic Suspension Control ............... ............................... ................................ ................................ ............................... ............................... .................................. .................. 42 Cornering Corner ing ........ ................. ................. ................. ................. ................. .................. ................. ................. ................. ................. ................. ................. ................. ................. ................ ....... 43 Air Suspension Components ............... ............................... ................................. ................................. ................................ ................................ ................................... ................... 44 Warning Lamp (K134) (K134) ................... ....................................... ........................................ ........................................ ......................................... ...................................... ................. 44 Control Contr ol Module (J197 (J197)) ........ ................. ................. ................. .................. ................. ................. ................. ................. ................. ................. ................. ................. ............... ...... 44 Levelingg Sende Levelin Senders rs (G76 (G76,, G77, G78 and G289 G289)) ........ ................ ................. ................. ................. ................. ................. ................. ................. ............... ...... 45 Air Springs .................... ......................................... ......................................... ........................................ ........................................ ......................................... ................................ ........... 46 Air Compressor ................... ....................................... ......................................... ......................................... ........................................ ......................................... ........................... ...... 47 Temper emperature ature Senso Sensorr (G29 (G290) 0) ........ ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................ ....... 48 Solenoid Soleno id Valves ........ ................. ................. ................. ................. ................. ................. ................. .................. ................. ................. ................. ................. ................. ................ ........ 48 Pressure Pressu re Senso Sensorr (G29 (G291) 1) ........ ................ ................. ................. ................. ................. ................. ................. ................. ................. ................. .................. ................. ............. ..... 48 Pressure Pressu re Accum Accumulator ulator ........ ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................. ................ ........ 49 Test Your Know ledg e
Teletest ................... ..................................... ..................................... ...................................... ...................................... ...................................... ........................................ ................................. ............ 51 Answer Worksheet ............... ................................. ................................... ................................... ................................... ................................... ....................................... ......................... .... 55
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HANDLING CONTROL SYSTEMS NOTES:
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ANTI-LOCK BRAKING SYSTEMS SYSTEMS ANTI-LOCK BRAKING ANTI-LOCK BRAKING SYSTEMS (ABS) Introduction One of the most significant safety advances in automotive engineering in recent decades are Anti-Lock Braking Systems (ABS). Vehicles Vehicles equipped with today’ t oday’ss modern anti-lock brake and traction assist systems, provide drivers with better braking and steering control in situations were traction is reduced or lost. Audi introduced introd uced ABS in in 1984 on the Audi 200. Anti-lock brake systems can provide fast and effective vehicle braking under critical braking conditions such as: • Wet or or slip slippe pery ry roa roadd surf surfac aces es • Ob Obst stac acle le avoi avoida danc ncee maneu maneuve vers rs • Pa Pani nicc or or eme emerg rgen ency cy st stop opss
These critical braking conditions, when encountered without ABS, may lead to wheel lock, which can cause wheel slip. Wheel slip often results in loss of steering control and increased stopping distances. ABS can help prevent wheel slip, and help drivers to maintain steering control and vehicle stability. stability.
Some early Audi ABS systems offered an ABS on/off switch.
SSP207/42
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ANTI-LOCK BRAKING SYSTEMS Introduction - continued Audi research and testing have shown that maximum braking force is transmitted to each wheel when a wheel slip range of approximately 8% to 35% is obtained, depending on the road surface and the type of tires being used. Wheel slip can occur during vehicle acceleration and deceleration. ABS will NOT shorten braking distances under all circumstances. When driving on gravel or newly fallen snow on top of icy surfaces, braking distances may be increased.
Operating range of the ABS
ABS and and its related tractio tractionn assist assist syssystems rely on the proper operation of the mechanical and hydraulic portions of the conventional brake system. Any malfunction of the con ventional vention al brake brake system system will will cause cause ABS to to not operate correct correctly ly.. When diagnosing an ABS or related system concern, always start with an inspection of the conventional brake system. This inspection should include: • Bra Brake ke flui fluidd level level and flu fluid id condition • Ti Tire re press pressure, ure, tir tiree size, size, and and tiree con tir condit dition ion • Bra Brake ke pad pad and rot rotor or condi conditio tionn • Su Susp spen ensi sion on condi conditition on • Br Brak akee lines lines an andd hose hose • Pro Proper per hand handbrak brakee adjus adjustme tment nt
Transmitted braking force on d ry conc oncrete rete surface
Roll olling ing w heel
Locked w heel
0% 8%
2
35%
W he he e l slip
100%
ANTI-LOCK BRAKING SYSTEMS SYSTEMS System Abbreviations Since Audi uses so many handling control systems that sound alike, abbreviations can be confusing. The following summarizes the most commonly used systems: — ABS (Anti-lock Braking System)
This system prevents the wheels from locking during critical braking maneuvers, allowing the driver improved brake effect, track stability and steering control. — ASR (Anti-Slip Regulation)
This system inhibits drive wheel spin on FWD vehicles while accelerating by intervening with the engine management system and applying brake pressure to the drive wheels.
— EBD (Electronic Brake Pressure Distribution)
— EDL (Electronic Differential Lock)
This system makes it possible to drive on road surfaces where each wheel has a different degree of traction by braking the wheell that whee that is spi spinnin nning. g. This acti action on send sendss the the power/torque to the wheel with the most traction. — ESP (Electronic Stabilization Program)
This system helps to control the vehicle in critical maneuvers, such as negotiating curves, by preventing the wheels from losing traction. This is done by intervening withh the wit the engine engine mana manageme gement nt syste system m and and applying brake pressure to the wheels.
This system prevents over-braking of the rear wheels due to load/weight shift. EBD takes the place of the previously used mechanical brake pressure regulator (load sensing valve).
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ANTI-LOCK BRAKING SYSTEMS Introduction to Audi ABS Systems All late model Audi vehicles use one of the following versions of anti-lock braking systems: • Bo Bosc schh 2S, 2S, FWD FWD mode models ls are are 4-ch 4-chann annel el,, Quattro models are 3-channel • Bo Bosc schh 5.0 5.0,, 4-c 4-cha hann nnel el • Bo Bosc schh 5.3 5.3,, 3-c 3-cha hann nnel el • Bo Bosc schh 5.3 5.3 wit withh ESP ESP,, 4-ch 4-chann annel el • Bo Bosc schh 5.7 5.7 wit withh ESP ESP,, 4-ch 4-chann annel el • Tev eves es MK 20 IE IE,, 4-c 4-cha hann nnel el • Tev eves es MK 60 60,, 4-c 4-cha hann nnel el System Application Chart Vee h i cle V
Cabriolet A4
M o d e l Ye a r 1996
1997
1998
Bosch 2S
Bosch 2S
Bosch 2S
Bosch 5.01
Bosch 5.0
Bosch 5.32
1999
2000
2001
Bosch 5.32
Bosch 5.32
Bosch 5.32,7
Bosch 5.7
Bosch 5.33
Bosch 5.33
Bosch 5.7
Bosch 5.32
Bosch 5.32,6
Bosch 5.7
Bosch 5.05
Bosch 5.33
Bosch 5.7
Bosch 5.33
Bosch 5.7
S4 A6
Bosch 2S
Bosch 5.0
S6
Bosch 5.0
Bosch 5.0
A8
Bosch 5.0
Bosch 5.32,4 Bosch 5.32
Bosch 5.0
Bosch 5.0
S8 TT
Teves Teves MK 20 IE2,6 MK 20 IE2,6,8 Bosch 5.33
Allroad Quattro 1. EDL optional 2. FWD vehicles equipped with EBD, EDL and ASR. AWD vehicles equipped with EBD and EDL 3. Equipped with EBD and EDL 4. A6 Wagon equipped with Bosch 5.0 5. Bosch 5.3 ABS with EDL optional 6. ESP optional 7. Bosch 5.7 with ESP optional 8. Running production change to Teves MK 60
4
2002
Teves MK 602 Bosch 5.7
ANTI-LOCK BRAKING SYSTEMS SYSTEMS Basic Operation of ABS With a vehicle equipped with conventional brakes, the driver must pump the brakes to help prevent skidding. When the vehicle is equipped with ABS, the driver keeps a firm foot on the brake, allowing the system to automatically pump the brakes, much faster than the driver possibly can. Because the wheels don’t lock, drivers have the increased ability to steer around hazards if they are unable to stop.
During braking, the ABS control module determines if one or more wheels have begun to lock up by comparing the rate at which the wheels are rotating. As soon as the difference in rotational speed indicates wheel lock-up, ABS will modulate hydraulic pressure to the affected wheel’s brake caliper.
When ABS is activated, the driver may hear the sound of the system working, and feel some pulsation or increased resistance in the When a driver operating an ABS equipped brake pedal. This sound and feel are actually vehicle steps firmly on the brake pedal, ABS the ABS hydraulic unit relieving and applying automatically modulates the brake pressure at pressure within the brake calipers. all four wheels to prevent wheel lock-up and ABS remains activated until normal braking maximize braking efficiency. (braking without ABS intervention) can be ABS modulates brake pressure using a resumed without the risk of wheel lock-up. hydraulic unit and return pump, which are both controlled by the ABS control module It is important that the driver keep (J104). firm pressure on the brake pedal when ABS is activated for the system to be effective.
W i th t h o u t A BS BS
W i th th A B S
5
ANTI-LOCK BRAKING SYSTEMS Common ABS System Components All of the anti-lock braking systems include the following components: • Whe Wheel el Sp Speed eed Sen Senso sors rs (G4 (G44, 4, G45 G45,, G46 G46 and G47) • ABS ABS Con Contr trol ol Mo Modu dule le (J (J10 104) 4) • Hy Hydra drauli ulicc Uni Unitt (DI (DIN N numb number er vari varies es depending on design) • Br Brake ake Sy Syst stem em Warn arnin ingg Li Light ghtss (K47 and K118)
Sensors
Operation of the anti-lock braking system relies on the integrity of the conventional hydraulic brake system. The master cylinder must be able to generate several hundred pounds per square inch of pressure, and the remainder of the brake system must be able to maintain that pressure without leaking. It is therefore important that the conventional brake system be in good working order for the ABS system to function f unction properly.
ABS/EDL control module J104
Actuators
ABS hydraulic pump V39
Front left + right speed sensor G45/G47
Rear left + right speed sensor G44/G46
Hydraulic unit with solenoid valves N99-102/ N133-136 N166-168
ABS warning lamp K47 Brake light switch F
Additional signals, e.g., time signal
Braking system warning lamp K118
Additional signals Diagnostic connection
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ANTI-LOCK BRAKING SYSTEMS SYSTEMS Common ABS System Components - continued Different variants of anti-lock braking systems are used depending upon the braking-forcedistribution concept of the vehicle. Two Two variations of ABS are used to control brake pressures in Audi vehicles: • 4-C 4-Chan hannel nel Sy Syste stem m – Bo Bosc schh 2S 2S (FW (FWD D models), Bosch 5.0, 5.3 with ESP, ESP, and 5.7, 5 .7, Teves MK 20 IE and MK 60 • 3-Chan 3-Channel nel Sy Syste stem m – Bos Bosch ch 2S 2S (Quat (Quattr troo models) and Bosch 5.3
The 4-channel control anti-lock braking system permits individual control of wheel-brake pressures. This is accomplished by using a solenoid-operated hydraulic-control valve for each of the vehicle’s vehicle’s wheel-brake circuits. The 3-channel control system regulates the brake pressures to each front wheel independently and to the rear wheels simultaneously simultaneously.. With this th is control contr ol system, syste m, one solenoids olenoidoperated hydraulic-control valve is used for each front wheel-brake circuit, along with a single hydraulic control valve that regulates the brake pressure to both rear wheels.
ABS Control Control Variations Variations
3-Channel 4 Sensors Front - Rear
4-Channel 4 Sensors Front - Rear Diagonal
Control Channel
Sensor
7
ANTI-LOCK BRAKING SYSTEMS Wheel Spe Wheel Speed ed Sen Sensor sorss (G44, G45, G46 and G47)
All anti-lock braking systems use wheel speed sensors to determine each wheel’s wheel’s rotating speed. Wheel speed sensors provide alternating current (AC) signals to the ABS control module. Wheel speed sensors are composed of a permanent magnet and a coil. Wheel speed sensors use a sensor ring or toothed rotor, rotor, commonly known as a trigger wheel. The trigger wheel can be mounted to the brake rotor rotor,, wheel bearing assembly assembly,, or it can be part of the constant velocity (CV) joint. The wheel speed sensor is mounted in the spindle. As the trigger wheel turns, the tip of the wheel speed sensor faces alternately a tooth on the trigger rotor and then a gap. This causes the magnetic field in the wheel speed sensor to change repeatedly repeatedly,, inducing an AC voltage signal. This signal changes proportionally with the speed of the wheel.
W heel Speed Speed Sens ensor or Designs
Trigger wheel
Pole plate M ag netic core Housing W ire core core Tip Permanent magnet
Trigger w heel Coil
8
Pole plate
ANTI-LOCK BRAKING SYSTEMS SYSTEMS Wheel Spe Wheel Speed ed Sen Sensor sorss (G44, G45, G46 and G47) - continued
Front W heels Trigger w heel
The gap between the wheel speed sensor and the trigger wheel is only about 1 millimeter. This precise tolerance must be maintained to ensure reliable AC voltage signals.
W heel spindle spindle
Drive axle
The ABS control module compares the voltage of the wheel speed spee d sensors to each other other.. If the voltage between the wheel speed sensors varies too much during normal driving conditions, a fault (DTC) will be set for the sensor that is out of the normal operating range. Normal operating voltage should not vary between the sensors by more than 0.15 volts when when wheel speeds speeds are equal. equal.
W heel speed speed sensor
Rear W heel heelss Speed sensor trigger
W heel speed speed sensor
AC Volta Volta ge Signal Scann Sc ann ing freq uency To control unit Test Instruments DSO 2 V/Div .= V/Div .=
Auto Mode 10ms/Div .
W h e el el speed sensor
Freeze Frame
Channel A
Channel B
Trigger mode 0
T
Time/Div.
Multimeter
Position
Go to
Adjustment of scanning scanning frequency
Measuring mode
Trigger wheel Print
Help
Shifting of curve
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ANTI-LOCK BRAKING SYSTEMS ABS Con Contr trol ol Mod Module ule (J1 (J104) 04)
The ABS control module receives, amplifies and filters wheel speed sensor signals to determine wheel speeds, brake slip, and rates of vehicle acceleration and deceleration. The control module then determines the amount of hydraulic brake pressure that should be applied to each wheel and sends output commands to the flow-restricting solenoidoperated valves within the hydraulic unit to control braking force.
Address Word Word 03 is used to access the ABS Control Module.
The ABS control module can effectively change hydraulic brake pressures for a wide variety of road surface conditions, such as dry, wet, icy or loose surfaces. The control module can also compensate for a mix in these road conditions, such as when one wheel is on ice, and the other wheels are on wet or dry road surfaces.
Toothed rotor
Warningg lights Warnin
Wheel speed sensor G45
K47
G44
K118
Control module
J104 V64
Hydraulic unit
N55
F
Brake switch
G47
Anti-lock Braking System ABS ITT/Mark 20 IE
10
G46
Brake circuit
Output signals
Brake circuit
Input signals
ANTI-LOCK BRAKING SYSTEMS SYSTEMS ABS Con Contr trol ol Mod Module ule (J1 (J104) 04) - cont continu inued ed
For safety, the ABS control module uses redundant microprocessors to analyze, calculate and compare input data and output commands. One processor serves as a control channel, and the other processor serves as a test channel. If ever the input data and output commands don’t agree, ABS becomes disabled and the braking system functions as a conventional brake system without ABS. The signal-process section of the ABS control module filters the A/C voltage signals from the wheel speed sensors and amplifies them. The analog sinusoidal A/C voltage is then converted to a square-wave output signal. The logic section further refines the wheel speed sensor signal, compensating for such variables variab les as tire t ire size and varyin va ryingg wheel speeds during cornering. The logic section uses this information to determine a vehicle
reference speed. From this baseline data, the logic section can then determine wheel deceleration/acceleration and wheel slip values. With this comparative information, it can then generate output signals to the hydraulic modulator as necessary necessar y. The safety circuit provides a fail-safe mechanism — a kind of checks and balances system — to double-check the logic section’s section’s analysis of signal input. The logic section’ section’ss measured reference speed and calculated output values to the hydraulic modulator are reviewed by the safety circuit to see if they “match.” If the safety circuit detects a flaw in the decisions made versus the input information received, a Diagnostic Trouble Code (DTC) is set in the ABS control module memory and ABS operation is disabled.
ABS Control Module Module
Actuators
Sensors
LOGIC SECTION TEST Wheel speed sensors
SAFETY CIRCUIT
SIGNAL PROCESS SECTION
CONTROL
SAFETY CIRCUIT
COOLING STAGE TO PREVENT BRAKE OVERHEATING
Solenoid valves
Power supply relay Battery
FAULT MEMORY
Return flow pump relay ABS warning light
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ANTI-LOCK BRAKING SYSTEMS ABS Con Contr trol ol Mod Module ule (J1 (J104) 04) - cont continu inued ed
The ABS control module stores braking system related DTCs in the order in which they occur occur,, until they are intentionally erased. The ABS control module’s module’s memory is nonvolatile, which means, any stored DTCs will NOT be erased when battery power is disconnected. Any stored brake DTCs can be retrieved from the control module, even if the module has been disconnected for an extended period of time.
ABS// EDL control ABS control mo dule J104
12
In the event of high brake system temperatures (caused by repeated severe EDL operation), the safety circuits within the ABS control module may deactivate EDL control. EDL will become operational again once the ABS control module recognizes a brake temperature within a specified range. This is done to eliminate the risk of overheating the brakes.
ANTI-LOCK BRAKING SYSTEMS SYSTEMS Hydraulic Unit
The hydraulic unit modulates brake pressure to the brakes by using solenoid-activated valves and an electric hydraulic pump. The ABS control module operates the solenoid valves and hydraulic pump during an ABS braking event. The ABS hydraulic unit is located in the engine compartment, near the master cylinder and consists of: • Valve block
If at this point the wheel remains locked, or is decelerating too quickly q uickly,, the ABS control module sends another command to the hydraulic unit to open the normally closed dump/outlet solenoid valve for that brake circuit. This action releases any pressure from the wheel’s wheel’s brake circuit.
• Hydraulic pu pump The valve block contains the solenoid valves that allow or restrict the flow of brake fluid through the wheel’s brake circuit as required when braking. If the driver applies the brakes hard enough to cause a wheel to lock-up, the ABS control module sends an output command to the hydraulic unit to activate the solenoid that controls the isolation/inlet valve for the locking wheel’ss hydraulic circuit. The isolation/inlet wheel’ valve cuts off fluid flow to prevent any more hydraulic pressure from reaching the wheel’s wheel’s As the hydraulic brake pressure is released brake caliper. from the wheel’s brake circuit, the hydraulic pump transmits the released brake fluid through an accumulator. The accumulator absorbs any pressure surges that occur as the brake fluid is discharged. From the accumulator,, the brake fluid tor f luid is pumped back into the master cylinder. cylinder. This action ensures that the master cylinder always contains a sufficient amount of brake fluid, so that the driver must only hold the brake pedal down during an extended ABS braking event. ABS cycles between holding, releasing and applying pressure individually at each brake caliper until ABS intervention is no longer needed and normal braking can occur without the risk of wheel lock-up.
13
ANTI-LOCK BRAKING SYSTEMS Hydraulic Unit - continued
Different traction situations require more or less cycling of the valves. On dry pavement the valves may only cycle one or two times to prevent wheel lock-up. However However,, on ice the valves may cycle up to ten times per second to prevent the wheels from locking-up. On 3-channel control ABS, rear wheel braking pressure is determined by using the select-low principle. When braking, the ABS control module uses the rear wheel with the greatest amount of slip to determine the amount of brake pressure required at both rear wheels. If a rear wheel begins to slip, the amount of brake pressure supplied to the slipping wheel is automatically applied to both rear wheels. The hydraulic unit is not serviceable and can only be replaced as an assembly. assembly. The reason for this is that the valve block must be able to withhold pressures of up to 5075 psi (350 bar) and it contains precision-made springs, seals, seats and solenoid valves, that during assembly,, require exact fit assembly f it and careful adjustment using special test equipment.
Bosch 5.3 Hydraulic Unit
14
Teves MK 20 IE Hydraulic Unit
ANTI-LOCK BRAKING SYSTEMS SYSTEMS Brake System Warning Lights
Brake system warning lights illuminate to alert the driver to various brake system conditions and are usually located on the instrument cluster. Each time the vehicle is started, the ABS control module performs a diagnostic selfcheck of the ABS system. During this self-check the ABS warning light (K47) in the dash panel insert (J285) will illuminate for a short period of time (up to six seconds). After the self-check has been completed, the ABS warning light will go out. If a malfunction is detected within the anti-lock braking system during the diagnostic selfcheck, the ABS warning light will illuminate and remain ON and ABS will be turned OFF OFF,, until the cause of the malfunction is repaired. However,, the conventional braking system will However remain fully operational.
K47
K118
The brake warning light (K118) will illuminate if the brake fluid level becomes low or if the parking brake is engaged. During the ABS diagnostic selfcheck, the brake pedal switch circuit is not tested. The warning light may still illuminate and then go out normally during the selfcheck, even if a brake light DTC is stored in the ABS control module’s module’s memory.
15
ANTI-LOCK BRAKING SYSTEMS NOTES:
16
TRACTION ASSIST SYSTEMS TRACTION ASSIST SYSTEMS Description and Operation Electronic Brake Pressure Distribution (EBD)
Some Audi anti-lock braking systems incorporate a feature called Electronic Brake Pressure Distribution (EBD).
When applying the brakes with the vehicle turning, EBD adjusts the brake pressure to the rear wheels. When driving on curves, if the difference in wheel speeds between the front EBD replaces the mechanical brake-pressureand rear, rear, or left to right wheels becomes too proportioning valve found on some braking high, EBD reduces the hydraulic brake systems by using software in the ABS control module. The software assesses the amount of pressure to the rear brakes by cycling the ABS inlet valve. This action limits the amount of traction at each wheel and electronically brake pressure applied to the rear wheels, distributes the brake pressure to the rear wheels accordingly. accordingly. The range of EBD control which helps ensure that the rear wheels do not become “over-braked.” ends when ABS control is applied. EBD supplements the standard ABS functions on: • Bosch 5.3 AB ABS • Bosch 5.7 AB ABS • Tev evees MK MK 20 20 IE IE AB ABS • Teves MK MK 60 60 AB ABS EBD uses the wheel speed sensors for wheel speed input. Detecting wheel speed differences between the individual wheels allows EBD to determine whether the vehicle is traveling straight ahead or turning. EBD can also determine any differences in tire wear and friction of the road surface. When driving in a straight line, EBD allows allows maximum braking pressure to reach the rear wheels. This helps ensure that the shortest stopping distances are obtained.
Braking in a corner (average retardation) Braking pressure plotted against time 100 (bar)
e r u s s e r P g n i k a r B
Braking pressure, front axle, time(s) 2.0 Braking pressure, rear axle, with EBD Braking pressure, rear axle, with mechanical braking pressure reducer
17
TRACTION ASSIST SYSTEMS Electronic Differential Lock (EDL)
Electronic Differential Lock (EDL), is a lowspeed traction assist system that acts automatically without the driver’s intervention. EDL uses many of the ABS components to adjust drive wheel speed for improved traction, steering control and stability stability.. EDL operates during acceleration up to speeds of: • 25 mph mph (40 (40 km km/h) /h) – fron front-w t-whee heell dri drive ve (FWD) vehicles • 50 mph mph (80 (80 km km/h) /h) – all all-w -whee heell driv drivee (Quattro) vehicles EDL supplements the standard ABS functions on: • Bosch 5. 5.0 ABS • Bosch 5. 5.3 ABS • Bosch 5. 5.7 ABS • Tev eves es MK 20 20 IE IE AB ABS • Teves MK MK 60 60 AB ABS To prevent the drive wheels from spinning during low speed acceleration, EDL monitors the drive wheels using the wheel speed sensors.
18
If excessive drive wheel spin is detected, the self-priming pump in the hydraulic unit extracts brake fluid from the master cylinder reservoir reser voir,, then pumps the fluid through a solenoid valve and into the brake caliper of the wheel with the highest rotation rotation rate. As a result, the drive torque is transmitted through the differential to the drive wheel with the most traction.
If EDL is under extreme use, the system will be temporarily disabled to prevent the brakes from overheating.
TRACTION ASSIST SYSTEMS Anti-s Ant i-slip lip Reg Regula ulatio tion n (ASR (ASR))
Wheel spin can also be controlled using a ASR can ASR can be sw swititche chedd ON or OF OFFF by pr press essin ingg the traction assist system known as Anti-slip ASRR bbutt AS utton on (E (E256 256). ). How Howeve everr, whe whenn the the ig ignit nitio ionn isis Regulation (ASR). ASR uses the vehicle’ vehicle’ss anti- cycled, ASR will automatically be switched ON. lock braking system and engine management ASRR shou should ld no norma rmallllyy be lef leftt ON. ON. AS ASRR sho should uld system to inhibit drive wheel spin during initial AS only be switched OFF in certain circumstances or moving acceleration. where wh ere wh wheel eel spi spinn can off offer er adv advant antage ages, s, such such as: ASRR isis onl AS onlyy ava availilabl ablee on FW FWD D veh vehic icles les and can • Whe Whenn drivi driving ng usin usingg the com compac pactt spare spare tire tire be incorporated into the following systems: • Whe Whenn rocki rocking ng the the vehi vehicl clee back back and and fort forthh • Bosch 5.3 ABS • Whe Whenn start startin ingg off off on an uphi uphillll gra gradie dient nt • Bosch 5.7 ABS wheree the wher the amount amount of trac tractio tionn isis sever severely ely • Tev evees MK MK 20 20 IE IE AB ABS reduced on one side of the vehicle • Teves MK MK 60 60 AB ABS When ASR is switched OFF, OFF, the ASR indicator light (K155) remains illuminated. ASRR wor AS works ks by ada adapti pting ng dri drive ve whe wheel el sp speed eedss and engine torque to a level that corresponds with the available traction on the road surface. ASR takes To ensure that ASR works properly, advantage of the EDL function to slow down a all four wheels must be fitted with spinning wheel, then sends a message through the identical tires. Any differences in can-bus to the powertrain control module (PCM). The PCM then tries to keep excessive wheel spin the rolling radius of the tires can under control by: cause ASR to t o reduce engine power power.. • Adj Adjust usting ing thr throt ottle tle val valve ve posi positio tionn • Reta Retard rdin ingg ign ignititio ionn tim timin ingg • Sup Suppre pressi ssing ng indi individ vidual ual inje injecto ctorr pulse pulsess
ASR Indicator Indicator Light (K155)
ASR Control Control Switch(E256)
19
TRACTION ASSIST SYSTEMS Electronic Stability Program (ESP)
The Electronic Stability Program (ESP) recognizes when the vehicle is in danger of skidding and automatically compensates if the vehicle breaks traction. ESP is a traction assist system that operates across the vehicle’s vehicle’s entire speed range.
Withou Wit houtt ESP ESP
ESP uses many of the ABS components, along with several additional components, to adjust drive wheel speeds in critical maneuvers such as curves in the road, or when an obstacle in the road must be suddenly avoided. ESP supplements the standard ABS functions on: • Bosch 5. 5.3 ABS • Bosch 5. 5.7 ABS • Tev eves es MK 20 20 IE IE AB ABS • Teves MK MK 60 60 AB ABS As the vehicle begins to move and accelerate, the wheels are prevented from losing traction by intervening with the engine management system to reduce engine torque and by applying brake pressure to the required wheels in order to allow the vehicle to pivot around an object or curve. For more information, refer to the Electronic Stabilization Program (ESP), Self-Study Program, Course Number 961903. Since ESP works in conjunction with ABS, ESP will be disabled disabled if there is any problem with the ABS system.
20
With Wit h ESP ESP
AUDI ABS SYSTEMS AUDI ABS SYSTEMS Bosch 2S ABS The Bosch 2S anti-lock braking system found on FWD models is a 4-channel design, using 3-position solenoid operated valves for each wheel brake circuit. This anti-lock braking system regulates brake pressure to each wheel independently.
Bosch 2S ABS does not have self-diagnositic capabilities and requires the use of ABS 2 Tester VAG V AG 1710.
The Bosch 2S anti-lock braking system found on Quattro models is a 3-channel design. This system uses three solenoid valves, one individual valve for each front wheel, along with one other solenoid valve to control the brake pressure at both rear wheels combined.
21
AUDI ABS SYSTEMS Bosch 2S ABS - continued All solenoid valves are of a directional control design with three hydraulic ports and three operating positions. This design allows the ABS control module to regulate the brake pressures between the th e master cylinder, cylinder, wheelbrake caliper and return circuit during the pressure build up, pressure hold and pressure reduction modes. The hydraulic unit is located near the brake master cylinder in the engine compartment, and the ABS control module, in most models, is located in the passenger compartment under the rear seat.
Sensors
ABS control module J104
Actuators
ABS hydraulic pump V39
Front left + right speed sensor G45/G47
Rear left + right speed sensor G44/G46
Brake light switch F
Hydraulic unit with solenoid valves N99-102/ N133-136 N166-168
ABS warning lamp K47
Braking system warning lamp K118 Additional signals Diagnostic connection
22
AUDI ABS SYSTEMS Bosch 5.0 ABS The Bosch 5.0 anti-lock braking system is a 4-channel system. This anti-lock braking system regulates brake pressure to each wheel independently using a 2-position solenoid valve for each wheel brake circuit. The hydraulic unit uses a single, small, lightweight aluminum valve block to contain the hydraulic solenoid valves. Each solenoid valve has only one energized position and is operated by the ABS control module. The hydraulic pump and ABS control module are attached to the valve block. The ABS hydrauli hydraulicc unit is located located near near the brake master cylinder in the engine compartment.
23
AUDI ABS SYSTEMS Bosch 5.0 ABS - continued Bosch 5.0 ABS can be equipped with Electronic Differential Lock (EDL). For more information on EDL, refer to Description and Operation of Traction Assist Systems (ESP), located in this publication.
Sensors
ABS/EDL control ABS/EDL control module module J104
Actuators Actua tors
ABS hydraul hydraulic ic pump V39
Front left + right speed sensor G45/G47 Rear left + right speed sensor G44/G46
Hydraulic unit with soleno solenoid id valves valves N99-102/ N133-136 N166-168
ABS warning warning lamp K47 Brake light switch F
Additionall signals, Additiona signals, e.g., time signal
Braking system warning warni ng lamp lamp K118 Additional Addit ional signa signals ls Diagnostic connection
24
AUDI ABS SYSTEMS Bosch 5.3 ABS The Bosch 5.3 anti-lock braking system used for vehicles not equipped with the driving dynamic control system called Electronic Stablization Program (ESP) is a 3-channel design. This hydraulic unit uses a single, onepiece valve block to contain the hydraulic solenoid valves. A pair of 2-position solenoidoperated valves (inlet and outlet valves) is used for each front wheel, along with one pair of solenoid operated valves to control the brake pressure at both rear wheels combined. A lownoise hydraulic pump is attached to the valve block. When equipped with EDL, lowtemperature performance of the EDL system is improved by using a pair of diaphragm outlet chambers, connected on the suction side (inlet) of the hydraulic valve blocks. These outlet chambers improve the flow of brake fluid under low temperature conditions, helping to prevent cavitation.
Front-wheel drive vehicles with Bosch 5.3 ABS are equipped with Electronic Brake Pressure Distribution (EBD), Electronic Differential Lock (EDL) and Anti-slip Regulation (ASR). Quattro (all-wheel drive) vehicles are equipped with EBD and EDL only. For more information, refer to Description and Operation of Traction Traction Assist Systems, located in this publication.
Diaphragm outlet chambers
25
AUDI ABS SYSTEMS Bosch 5.3 ABS - continued Vehicles equipped with Bosch 5.3 with ESP use Vehicles a 4-channel design anti-lock braking system. ESP helps to control the vehicle in critical maneuvers such as negotiating curves in the road. As the vehicle begins to yaw and rotate, the wheels are prevented from losing traction by intervening with the engine management system and applying brake pressure to the wheels. To prevent pump cavitation when equipped with ESP, ESP, the suction pressure of the Bosch 5.3 hydraulic pump is improved by the use of an additional ESP charge pump. Use of the charge pump is necessary due to the singlestage design of the hydraulic pump of the Bosch 5.3 system.
Sensors
ABS control module J104
Actuators
ABS hydraulic pump V39 Front left + right speed sensor G45/G47
Rear left + right speed sensor G44/G46
Hydraulic unit with solenoid valves N99-102/ N133-136 N166-168
ABS warning lamp K47 Brake light switch F
Additional signals, e.g., time signal
Brake system warning lamp K118 Additional signals Diagnostic connection
26
AUDI ABS SYSTEMS Bosch 5.3 ABS - continued With the single-stage hydraulic pump, the entire suction volume must flow through the suction line during one piston stroke (from TDC to BDC) into one chamber ch amber.. With this type of pump, suction pressure is high. When the ambient temperature decreases, suction pressure rises even further as the viscosity of the brake fluid increases. The result of high suction pressure is cavitation and the associated drop in performance on the pressure side of the pump.
With Bosch 5.3 ABS, output tests may be performed to conduct a function check of the hydraulic pump and solenoid valves. ESP operates across the entire speed range. Since ESP works in conjunction with ABS, ESP will be disabled if there is any problem with with the ABS system. For more information, refer to the Electronic Stabilization Program (ESP), Self-Study Program, Course Number 961903. The ABS control module is directly attached to the hydraulic unit, except for vehicles equipped with ESP. ESP. For ESP equipped vehicles, the control module is located in the passenger compartment.
Single-stage ABS return pump suction volumes Suction volumes
UT
OT
OT = TDC
UT
OT
UT
UT = BDC
Suction volumes
UT
OT
UT
OT
UT
27
AUDI ABS SYSTEMS Bosch 5.7 ABS The Bosch 5.7 anti-lock braking system is a 4-channel system equipped with ESP. ESP. The hydraulic unit and control module form a single unit similar to the Bosch 5.3 anti-lock braking system with the addition of the following: • The sin singl gle-s e-stag tagee hydrau hydraulilicc return return pump pump (V39) has been replaced with a two-stage pump. • Brake Brake se servo rvo pre pressu ssure re sens sensor or (G29 (G294) 4) has has been added to detect emergency braking situations. Due to higher viscosity of the brake fluid at extremely low temperatures, the required delivery rate for the hydraulic return pump with ESP can not be achieved without the use of the additional charge pump (V156). ESP operation resulted in an increased suction resistance within the system.
28
AUDI ABS SYSTEMS Bosch 5.7 ABS - continued With a two-stage hydraulic pump, there are two working chambers that the piston acts upon. Suction is effected in two stages as the brake fluid is drawn through the suction line during each piston stroke (from TDC to BDC and from BDC to TDC). With this pump design, the entire suction volume is supplied to the pump almost continuously cont inuously,, creating a significantly lower suction flow rate, which diminishes suction pressure and prevents cavitation. This type of hydraulic pump ensures a quick pressure build up, even at extremely low ambient temperatures.
Two-stage ABS return pump suction volumes Working chamber 2 Suction volumes
Working chamber 1
UT
OT
OT = TDC
UT
OT
UT = BDC
Suction volumes
UT
OT
UT
OT
29
AUDI ABS SYSTEMS Bosch 5.7 ABS - continued The Bosch 5.7 hydraulic unit is also equipped with a new feature called the brake assist. During an emergency braking situation, the brake assist feature aids the driver by automatically increasing brake pressure to a level exceeding the wheel lock-up limit for all wheels. This action quickly brings ABS into into its operating range, thus achieving maximum vehicle deceleration. In order to detect emergency braking situations, a brake servo pressure sensor has been added to the hydraulic unit.
Pressure sensor G294
The brake servo pressure sensor monitors the pressure increase gradient of the brake system (build up of brake pressure as compared to time). If the brake pressure gradient exceeds a predetermined limit, the brake assistant feature is activated.
] p [ e r u s s e r P
Time [t] SSP254_092
Emergency braking Normal braking distance
30
AUDI ABS SYSTEMS Bosch 5.7 ABS - continued The function of the brake assistant feature takes place in two phases. The first phase begins if the brake pressure increase gradient exceeds a predetermined value (indicating emergency braking). During this first phase, the hydraulic return pump, along with the associated solenoid valve(s) within the hydraulic unit, become activated by the ABS control module. This is accomplished by using the ESP logic program, which increases the brake pressure into range of ABS control. This action is performed in a similar manner by the control system used for EDL. For more information, refer to Description and Operation of EDL, located in this publication.
Brake assistant activated
In the second phase, if the brake pressure being applied by the driver falls below the predetermined value after triggering the brake assistant feature (indicating emergency braking has ceased), brake system pressure is restored to the level of brake pedal pressure as applied by the driver. Inlet and outlet valves within the ABS hydraulic unit are no longer simply switched on and off (using a duty cycle). They are now regulated using a pulse-width modulated (PWM) voltage signal. This allows more precise control on extremely slippery surfaces, such as ice.
Brake pedal unloaded
Brake assistant switches off
Phase 2
Phase 1
] p [ e r u s s e r p e k a r B
Time [t]
SSP254_084
Brake pressure determined by an experienced driver Regulated brake pressure (brake assistant) Determined brake pressure insufficient inexperienced driver
31
AUDI ABS SYSTEMS Teves MK 20 MK 20 IE ABS The Teves Teves MK 20 IE anti-lock braking system is a 4-channel system. This ABS hydraulic unit incorporates an aluminum valve block and 2-position hydraulic solenoid valves. Each solenoid valve has only one energized position. The Inlet valves are of a design that allows better brake pressure regulation and an improved brake pedal feel. The hydraulic pump and ABS control module are attached to the valve block. The ABS hydraulic unit is located near the brake master cylinder in the engine compartment.
Teves MK 20 IE ABS can also be equipped equ ipped with a driving dynamic control system called Electronic Stabilization Program (ESP). ESP helps to control control the vehicle vehicle in critical maneuvers such as curves in the road. As the vehicle begins to yaw and rotate, the wheels are prevented from losing traction by intervening with the engine management system and applying brake pressure to the wheels. ESP operates across the entire speed range. Since ESP works in conjunction with ABS, ESP will be disabled if there is any problem with ABS. For more information, refer to the Electronic Stabilization Program (ESP), Self-Study Program, Course Number 961903.
Teves MK 20 IE ABS on front-wheel drive vehicles is equipped with Electronic Brake Pressure Distribution (EBD), Electronic Differential Lock (EDL) and Anti-slip Regulation The ABS hydraulic unit for vehicles equipped with ABS/EDL/ESP are larger than the control (ASR). Quattro (all-wheel drive) vehicles are unit used on vehicles equipped with ABS only: equipped with EBD and EDL. For more information, refer to Description and • AB ABSS onl onlyy – 5.1 5.1 in inch ches es (1 (130 30 m mm) m) Operation of Traction Assist Systems, located • AB ABS/ S/EDL EDL/E /ESP SP – 5.3 5.3 in inche chess (13 (135 5 mm mm)) in this publication.
32
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33
AUDI ABS SYSTEMS Teves MK 60 ABS Teves MK 60 ABS is a 4-channel system. Brake pressure is regulated to each wheel independently using 2-position solenoid valves val ves.. The Th e ABS A BS hydrau hy draulic lic unit u nit use usess a lightweight aluminum valve block of a compact design. The hydraulic pump and ABS cont control rol modu module le are a re atta a ttache chedd to the valve val ve block b lock.. The Th e ABS AB S hydrau hy draulic lic unit is located near the brake master cylinder in the engine compartment. Front-wheel drive vehicles with Teves MK 60 ABS are equ equippe ippedd with wi th Elect E lectroni ronicc Brake Br ake Pressure Distribution (EBD), Electronic Differential Lock (EDL) and Anti-slip Regulation (ASR). Quattro (all-wheel drive) vehicle veh icless are ar e equipp eq uipped ed with w ith EBD and EDL. For more information, refer to Description and Operation of Traction Assist Systems, located in this publication.
34
Teves MK 60 ABS can also be equippe equippedd withh a dri wit drivin vingg dyna d ynamic mic co cont ntrol rol syst system em called Electronic Stabilization Program (ESP). (ES P). ESP ESP helps to control the vehicle in critical maneuvers maneuvers such as cur ves in the road. As the vehicle begins to yaw and rotate, the wheels are prevented from losing traction by inter inter vening with the engine management system and a pplying brake pressure to the wheels. ESP operates across the entire speed range. Since ESP works in conjunction with ABS, ESP will be disabled if there is any problem with ABS. For more information, refer to the Electronic Stabilization Program (ESP), Self-Study Program, Course Cou rse Number 96 961 1903.
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35
AUDI ABS SYSTEMS ABS Ser Servic vice e If service to an ABS component becomes necessary, use the following guidelines when handling replacement components: • Dep Depend endin ingg on on app applilicat catio ion, n, aft after er replacement of an ABS control module, the module MUST be coded. Coding the ABS control module is necessary for the braking and traction assist systems to operate correctly. For a detailed description of the procedure, refer to AESIS. • Aft After er the the hydrau hydraulilicc porti portion on of the the brak braking ing system has been opened for any reason, the braking system MUST be bled. The brake bleeding procedure for vehicles equipped with ABS may be different than those for conventional brakes, and will vary betwe between en the the differ different ent avai availabl lablee ABS ABS systems. For a detailed description of the brake bleeding procedures, refer to AESIS. • Alw Always ays tran transpo sport rt repla replacem cemen entt compo componen nents ts in the original container. DO NOT unpack the components from the containers until you are read readyy to to imme immediat diately ely inst install all them them.. • DO NOT NOT dro dropp or pl place ace hea heavy vy obj object ectss on the replacement component and/or its packaging. • Dur Durin ingg inst install allati ation on of of a repla replacem cement ent hydraulic unit, pay CLOSE ATTENTION to the positioning of the brake lines. Failure to install the brake lines in the correct location willl lead wil lead to impr improper oper ope operati ration on and and possible damage of the braking system.
36
• When When inst install allin ingg a rep repla lacem cement ent AB ABSS hydraulic unit, DO NOT remove the shipping plugs from the hydraulic ports until you are immediately ready to install the brake lines. Failure to do so may result in brake fluid loss from within the hydraulic unit. Excessive brake fluid loss may cause the hydraulic unit to lose its prime, making brake bleeding very difficult, if not impossible. • ALW ALWA AYS make make sure any spec special ial servi service ce tools and diagnostic equipment that you may use when servicing ABS are in workin wor kingg order order.. • ALW ALWA AYS observ observee the rule ruless for cle cleanli anliness ness and safety when servicing ABS. Warning: Brake Brake fluid is
poisonous; BE poisonous; BE SURE that that safety glasses are worn when bleeding brakes or possible personal injury may occur. occur. Caution: Brake Brake fluid must NOT
come in contact with paint-work or possible damage may occur. occur.
4-LEVEL AIR SUSPENSION SYSTEM 4-LEVEL AIR SUSPENSION Introduction The 4-level air suspension system is designed to control the overall vehicle height. This system changes ground clearance by 2.6 inches (66mm) (66mm) in four four stages. The The four stages can be controlled manually or automatically.
The air suspension system is designed for fast response, low noise and the ability to protect the power supply of the vehicle.
The 4-level air suspension is composed of the following components: • 44-le leve vell con contr trol ol di disp spla lay y • Warning light • Air springs • Solenoid va valve vess • Pressure se sensor • Le Leve vellin ingg se send nder erss • Air compressor • Tem empe pera ratu ture re se sens nsor or • Accumulator
Rear Right Vehicle Leveling Sender
Rear Right Air Suspension Strut Strut
Control Unit
Air Suspension Control Display Pressure Accumulator
Front Right Air Suspension Strut Strut
Rear Left Vehicle Leveling Sender Rear Left Air Suspension Strut Electric/Pneumatic Lines
Front Right Vehicle Leveling Sender Front Left Vehicle Leveling Sender
Air Supply Unit
Front Left Air Suspension Strut
37
4-LEVEL AIR SUSPENSION SYSTEM Air Sus Suspen pensio sion n Lev Levels els H e i g h t I n cr e a se Level 1
G r o u n d C le a r a n ce
5.6 inches
142 mm
Level 2
1 inch
+ 25 mm
6.6 inches
167 mm
Level 3
1 inch
+ 25 mm
7.6 inches
192 mm
Level 4
0.6 inches + 16 mm
8.2 inches
208 mm
Ground clearance 5.6 inches 142 mm
Level 1
Ground clearance 6.6 inches 167 mm
Level 2
Ground clearance 7.6 inches 192 mm
Level 3
Ground clearance 8.2 inches 208 mm
Level 4
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4-LEVEL AIR SUSPENSION SYSTEM Air Su Suspe spensi nsion on Con Contr trol ol Dis Displa play y The air suspension control display is located on the dashboard above the radio. The following is a description of how to operate the air controlled suspension system: The light emitting diode (LED) in the LED Display indicates the ride height. To To change between automatic and manual modes, press the Up or Down Control Button for two seconds. When manual mode is selected, the LED above the “man” inscription illuminates.
Down Control
LED Display
Up Control
In manual mode, vehicle ride height is increased by pressing the Up Control Button. If Up Control Button is pressed more than once, height can be increased in stages from the lowest level to the highest level. As the ride height is increasing, the LED Display shows the actual level as a steady light and the selected level as a flashing light. After pressing the Down Control Button, the vehicle drops to a lower level. The current level flashes in the LED Display and the selected level (not yet reached) is indicated by a steady light. Continuous flashing of an LED indicates the denial of a level request, for example, when speed is too high.
Manual mode, level 2 requested, vehicle currently in level 1.
Automatic mode, moving to level 1, vehicle currently in level 2.
Automatic mode, moving to level 3, vehicle currently in level 1.
Automatic mode, moving to level 4, vehicle currently in level 3.
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4-LEVEL AIR SUSPENSION SYSTEM Manual Suspension Control Conditions for Manual Operat Ope rating ing Mo Mode de
In manual mode, the suspension system allows When the engine is running, the vehicle can be raised as long as: the vehicle’s vehicle’s driver to determine de termine what height the vehicle is at. at . However, However, manual control does • The air air suspe suspensi nsion on compr compress essor or temp tempera eratur turee not allow the vehicle operator to override the is below 230 F (110 C) C).. basic height-to-speed settings. The vehicle will • Suffi Sufficie cient nt accumula accumulator tor pres pressure sure is pres present. ent. still automatically lower when a certain road There should be at least a 3 bar (44 psi) speed has been reached. difference between the pressure Pressing either the up or down button for accumulator and the air springs. about two seconds will switch the air suspension system between manual and When the engine is not running, the vehicle automatic modes. can be raised as long as sufficient accumulator pressure is present. The vehicle can be raised or lowered in manual mode as long as no relevant fault codes are stored in memory. °
°
Height decrease procedures
Level 4
Automatic lowering
Level 3 Possible manual control
Level 2 Level 1
0
22
50
75 Height increase procedures
Level 4
Automatic lowering
Level 3 Resetting only from level 3
Level 2 Possible manual control
Level 1
0
40
22
50
75
4-LEVEL AIR SUSPENSION SYSTEM Service (Jack) Mode
Hoist Mode
Before raising the Allroad Quattro on a hoist or jack, the vehicle should be put into the service mode. When the vehicle is put into service mode, air is not let into or out of the 4-level air suspension system.
The air suspension control unit goes into hoist mode if the height signal of a stationary vehicle is increased due to a lift or jack.
Service mode can be switched on or off by pressing and holding down both the up and down buttons for five seconds. When in service mode, the manual row of LEDs, the warning lamp and both the up and down buttons will illuminate.
The hoist mode prevents excessive ventilation of the air springs when the vehicle is raised for service. Lifting of the vehicle should be carried out as quickly as possible, so that the air suspension control unit clearly knows it should enter hoist mode.
The service mode will be automatically switched off when a road speed of approximately 6 mph (10 km/h) is exceeded. The service mode will not switch on if the hoist mode is recognized.
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4-LEVEL AIR SUSPENSION SYSTEM Autom Aut omat atic ic Su Suspe spens nsion ion Con Contr trol ol In automatic mode, the 4-level air suspension works without driver interaction. The air suspension system raises and lowers the vehicle according to the speed and level charts below. Level 4 Level 3
Height decrease procedures Automatic Autom atic lowering lowering
Level 2
After 30 30 seconds seconds
Level 1
0
22
50
Speed in mph
75 Height increase procedures when vehicle is commanded commanded to Level Level 3 or Level 4 after the ignition is on.
Level 4 Level 3
After 30 30 seconds seconds
Level 2
After 120 120 seconds seconds
Level 1 Raising immediately
05
22
43
75
Speed in mph Level 4 Height increase procedures when vehicle is in Level Level 3 or or Level 4 before the ignition is on
Level 3 Level 2
After 30 30 seconds seconds
Level 1
Raising immediately
0 19
42
37
43
75
4-LEVEL AIR SUSPENSION SYSTEM Cornering
If the vehicle is cornering, it will not raise or lower until it is through the corner, corner, even if it is in the process of changing the vehicle height. Instead, the height request will be stored and carried out when the vehicle is driving in a straight line. If the vehicle is accelerated quickly down a very twisty road, it is possible for the suspension to stay in a high position, regardless of road speed. In this case, the Electronic Stabilization Program (ESP) will activate, even if the driver had turned it off manually.. ESP remains activated until manually u ntil the suspension system has a chance to lower the vehicle.
No control when cornering
No control when cornering
Level 4 Level 3 Level 2 Level 1
0
22
43 50
75
Speed in mph
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4-LEVEL AIR SUSPENSION SYSTEM Air Sus Suspen pensio sion n Co Comp mpon onen ents ts Warning Warnin g Lamp (K134)
Control Module (J197)
When a fault occurs in the 4-level air suspension system, warning lamp (K134) illuminates.
The air suspension control module (J197) is the brain of the 4-level suspension system. The control module monitors air suspension inputs and commands the vehicle to raise or lower lower,, depending on road speed, vehicle height and driver requests.
Warning lamp operation: • Duri During ng sus suspens pension ion sys system tem fai failur lures es or when the system is disabled, the warning lamp will illuminate steadily unless fuses are missing or blown. • When When basi basicc syst system em sett settin ingg has has not not been been carried out successfully, the warning lamp will illuminate steadily. • Extreme Extremely ly low or hig highh level levelss will will cau cause se the warning lamp to flash. • Out Output put dia diagno gnosti sticc test test mod modee will will cau cause se the warning lamp to flash. W arnin arningg Lam Lam p K13 4
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The air suspension control module is located in the left rear of the vehicle, near the accumulator. Use Address Word 34 to access the air suspension control module.
4-LEVEL AIR SUSPENSION SYSTEM Leveling Senders (G76, G77, G78 and G289)
Leveling senders (G76, G77, G78 and G289) are inductive sensors that determine the angle of the surface they are mounted on. These sensors send this information to the suspension control module (J197). Both the suspension and the headlight range systems use different angle signals for operation. One signal output provides an angle-proportional voltage. A second signal output provides an angle-proportional pulse width modulated (PWM) signal. Each leveling sender provides both types of signals.
The 4-level air suspension system uses the PWM signal and the headlight range system uses the voltage signal. Power is supplied to the left side leveling sensors (G78 and G76) by the headlight range control module. Power is supplied to the right side leveling sensors (G289 and G77) by the suspension control module. This ensures headlight control will still operate even if the suspension control module fails.
Cut-a-way of Level Sender
Front Level Sender
Rear Level Sender
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4-LEVEL AIR SUSPENSION SYSTEM Air Springs
The air springs, which are located at both the front and rear of the vehicle, allow the changes in ground clearance and are made up of a reinforced bag that surrounds the shock absorbers. When the bag is pressurized, it rolls from the bottom to the top of the shock absorber and raises the vehicle.
Air Spring Components
Stop buffer
Tension ring
Inner protective layer
Cord layer 1
Cord layer 2
Outer protective layer
Piston
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4-LEVEL AIR SUSPENSION SYSTEM Air Compressor Compressor
Compressed air is generated by a single-stage piston air compressor with an integrated air dryer.
Special features of the 4-level air suspension system are: • Ma Maxi ximum mum ope operat rating ing pr press essure ure of 16 16 bar bar The compressor is dry-running, meaning that it (232 psi) does not use oil for its operation. This • Su Sucti ction on and and dis discha charge rge of air air pres pressur suree by eliminates any possible oil contamination in an air filter/noise damper located in the the air springs. spare tire housing During normal operation, the compressor will • Tempe emperatu rature re mon monito itoring ring by a tempe temperatu rature re only operate when the engine is running. The sensor located at the cylinder head following are air compressor operation exceptions: • Pr Press essure ure mo moni nitor torin ingg usin usingg a press pressure ure sensor located in the solenoid valve unit • Fi Fina nall con contr trol ol di diag agno nosi siss • Volt oltage age supp supply ly prot protecti ection on by only run runnin ningg • Ba Basi sicc sys syste tem m set settiting ngss the compressor when a sufficient amount of • The ig igni nitio tionn is on on and and the the syste system m detec detects ts an an electrical power is being produced from the extremely low ride height engine’ss electrical system engine’ s ystem
Compressor
Discharge valve
Air dryer
Motor
Vibration isolating isolating mount
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4-LEVEL AIR SUSPENSION SYSTEM Temperature Sensor (G290)
Pressure Sensor (G291)
The temperature sensor (G290) is attached to the cylinder head of the air compressor to determine the compressor temperature.
The pressure sensor (G291) is integrated into the valve unit, and is used to monitor both the accumulator pressure and the pressure to each air shock.
The temperature sensor sends a signal to the control unit (J197). The control unit determines if the signal is within normal operating range. If the signal is not within normal operating range, the air suspension compressor is shut off until an operating temperature within specifications is reached. Solenoid Valves
The 4-level air suspension system uses six solenoid-operated valves. The discharge valve (N111) is integrated into the dryer housing. The function of discharge valve is to both limit and retain pressure in the air suspension system.
The pressure sender provides a voltage signal to the suspension control unit that is proportional to the accumulator and shock pressures. If the compressor shuts down due to overheating, it may take up to 15 minutes before the compressor temperature becomes low enough for the pump to operate. Depending on ambient temperatures, the air suspension compressor takes approximately 1 hour to cool fully fully..
The four air shock valves (transverse check valves, N148, N149, N150 and N151) and the accumulator valve (N311) are combined into the solenoid valve unit which is located in front of the spare tire housing. All solenoid valves are of a directional design and are closed when without current.
From compressor
Solenoid Valve Unit
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4-LEVEL AIR SUSPENSION SYSTEM Pressure Accumulator
The pressure accumulator for the air suspension system stores compressed air for later use. If there is sufficient pressure in the pressure accumulator, accumulator, the vehicle can be raised without compressor assistance. Sufficient pressure means that the pressure accumulator must have at least 3 bar (44 psi) more pressure than the air springs have. The pressure accumulator is made of aluminum and has a capacity of approximately 1.7 gallons (6.5 liters). The pressure accumulator is filled by the compressor under two conditions: • Whe Whenn driv drivin ingg at a spe speed ed of of appro approxi xima matel tely y 22 mph (36 km/h) or above. This is done so that compressor noise is not noticeable. • Whe Whenn the the acc accumu umulat lator or do does es no nott have have enough pressure to raise the vehicle to the requested level.
While driving at road speeds below 22 mph (36 km/h), the air supply is primarily taken from the pressure accumulator (as long as sufficient pressure is present). While driving at road speeds above 22 mph (36 km/h), the air supply is primarily taken from the compressor. Maximum accumulator pressure is 16 bar (232 psi). Follow the procedure found in AESIS to properly bleed the pressure accumulator.
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4-LEVEL AIR SUSPENSION SYSTEM NOTES:
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Knowledge Assessment Knowledge Assessment An on-line Knowledge Assessment (exam) is available for this SSP. SSP. The Knowledge Assessment may or may not be required for Certification. Certification. You can find this Knowledge Assessment at: www.accessaudi.com
From the accessaudi.com homepage: – Click on the “ACADEMY” Tab – Click on the “Academy Site” Link – Click on the ”CRC Certification” Link
For assistance, please call: Audi Academy Learning Management Center Headquarters 1-877-AUDI-LMC (283-4562) (8:00 a.m. to 8:00 p.m. EST)
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