Table of Contents Introduction to DSC Subject
Page
Module Objectiv Objectives...................... es................................... ........................... ............................ ............................ ................. ...2 2 Overview of DSC Systems ..................................................................3 Puspose Puspose of of the System ................................ .............................................. ............................ ....................... ...........4 ..4 DSC Components omponents ............................ .......................................... ........................... ........................... ..........................9 ............9 C o n tro trol lM o d u le/H yd rau rau lic U n it............................................................. . 10 W h eelS p eed S en so rs ......................................................................... 11 11 H yd rau rau lic P res ressu re S en so r ................................................................ .. . 12 S tee teerin g A n g le S en so r ......................................................................... .. 1 3 R o tati tatio n R ate S en so r ...........................................................................14 .14 L atera teral lA ccelerati ratio n S en so r .................................................................16 .16 C o m b in ed R o tatio n R ate/L ateralA cceleratio n S en so r ..........................1 7 D S C S w itch ch .........................................................................................1 8 H an d b rak rake S w itch tch ...............................................................................1 8 B rak ake S w itch ch .......................................................................................18 18 H yd rau rau lic S ystem tem C o m p o n en ts ............................................................1 9
Principle Principle of of Operation Operation ............................... ............................................. ............................ ....................... ..............2 .....24 4 Diagnosis ........................... ........................................ ........................... ............................ ............................ ..................... ............2 .....29 9 Review Questions ........................... ........................................ ........................... ............................ ..................... ............ 31
1 Introd uc tion to D S C
Model: Model:
1995-1997 E38 750iL, E31 850Ci with with DSC II 1998 E38 740i/iL and 750iL, E39 540i with DSC III 5.3 1999-Present E38 740i/iL and 750iL, E39 540i and 528i with DSC III 5.7
Production: Production: All E38 and E39 with Bosc Bosch 5.7 DSC III Objectives: A fter co m p leti etio n o f th is m o d u le yo u sho sh o u ld b e ab a b le to to : Understand Basic DSC operation.
Identify dentify Components Components w ithi thin the the DS DS C S ystem (DSC (DSC 5.3 and DS C 5.7) 5.7).
•
Lo c a t e C o m po po ne n e nt nt s w it it hi hin th th e D S C s y s te te m. m.
•
Un nd d e rs rs t a nd n d t he h e d if iffe re re nc nc e s b e tw t w e e n AS AS C a n d D S C .
•
Under Und erstand sta nd Dif Differen erences ces between b et ween Bos ch DSC DSC 5.7 and 5.3 5.3..
2 Intro d uc tion to D S C
Model: Model:
1995-1997 E38 750iL, E31 850Ci with with DSC II 1998 E38 740i/iL and 750iL, E39 540i with DSC III 5.3 1999-Present E38 740i/iL and 750iL, E39 540i and 528i with DSC III 5.7
Production: Production: All E38 and E39 with Bosc Bosch 5.7 DSC III Objectives: A fter co m p leti etio n o f th is m o d u le yo u sho sh o u ld b e ab a b le to to : Understand Basic DSC operation.
Identify dentify Components Components w ithi thin the the DS DS C S ystem (DSC (DSC 5.3 and DS C 5.7) 5.7).
•
Lo c a t e C o m po po ne n e nt nt s w it it hi hin th th e D S C s y s te te m. m.
•
Un nd d e rs rs t a nd n d t he h e d if iffe re re nc nc e s b e tw t w e e n AS AS C a n d D S C .
•
Under Und erstand sta nd Dif Differen erences ces between b et ween Bos ch DSC DSC 5.7 and 5.3 5.3..
2 Intro d uc tion to D S C
Overview of DSC Systems Model Ye Year
1998
1999
E36
E36/7 Z3
E46
E39
E38
E53
E52
E65 E66 E66
E85 E85
AS C+ C+ T
AS C + T MK IV G
N/A
9/97 AS C + T5 S : 528i 528i
9/97 DSC III Bos ch 5.3 5.3
N/A
N/A
N/A
N/A
DSC III 5.3 S : 540i 540i N/A 528i
S : 740i/iL S : 750iL 750iL
9/98 AS C + T5 S : 528i 528i
3/98 N/A Bosch DS C III 5.7
N/A
N/A
N/A
Bosch DSC III 5.7 S : 540i 540i O: 528i
S : 740i/iL S : 750iL 750iL
AS C + T AS C + T AS C MK IV G MK 20 EI Te ve s 328iC (Except M) MK 20 EI 318ti AS C + T Mk IV G (M Versions)
2000
N /A
fro m 4/99 4/99 Te ve s MK 20 DSC III
DSC III Te ve s MK 20 EI from fro m 6/99
6/99 Bosch DSC III 5.7 S TD All
3/99 Bosch DS C III 5.7 S TD All
D S C III D S C III N/A B o s c hB o s c h 5.7 5. 7 5.7 9/99 1/00
N/A
2001
N /A
Fro m 9/00 9/00 Te ve s MK 60 DSC III
DSC III Te ve s MK 60 from fro m 9/00
D S C III Bosc h 5.7 5.7
D S C III Bos ch 5.7 5.7
D S C III D S C III N/A B o s c hB o s c h 5.7 5. 7 5.7
N/A
N/A
D S C III B o s c h 5.7 5. 7
N/A
N/A
D S C III D S C III DSC III B o s c h B o s c h Bosch 5.7 5. 7 5.7 5.7
M Versions Te ve s MK 20 D S C III
2002
N /A
2003
N /A
N /A
M3 Te ve s MK 20 E46/16 AWD Bosch DSC III 5.7 Same D S C III as Bosc h 5.7 5.7 2001 Same as 2001
D S C III Bosc h 5.7 5.7
DSC III Bosch 5.7
DSC III Te ve s MK60
S = STANDARD EQUIPMENT O = OPTIONAL EQUIPMENT STD All = Standar Standard d All Models
3 Introd uc tion to D S C
Dynamic Stability Control (DSC II/DSCIII) Purpose of the System D S C ad ds a further dim en sion to the traction co ntrolsystem . D S C ad ds lateral co ntrolto this already proven system . The traction controlsystem w as designed for longitudinal stability and providing the optim um traction for driving off. D S C IIhas the ability to m ildly correct for lateralinstability and only at the rear brakes w hen braking co ntrolis necessary. D S C III has the ability to brake any w heelduring co rnering m aneu vers w here the control m odule’ s p rogram m ed lim its for veh icle oversteer an d understeer are exceed ed . The D S C IIsystem m onitors the inp ut values from the tw o front w heel speed sensors and the steering angle senso r. The rotational sp eeds of the front w heels for the g iven turning angle are co m pared to the p rogram m ed values in the D S C co ntrol m odule. If the values are outside the program m ed lim its, D S C regulation w illbe activated. N ew sensors are ad ded to the D S C III system to m onitor the rotational rate of the veh icle around its verticalaxis and a lateralacceleration senso r to m onitor the side to side forces on the vehicle. O n D S C II or D S C III system s, the co ntrolreg ulation follow s the sam e outputs as for traction controlregulation w ith: • Throttle valve regulation • Engine intervention • R ear brake control The co ntrolphases are brief and only occur long enough to co rrect the unstab le co ndition. The follow ing text in this training m anual w ill focus on B osch D S C III 5.3 and 5.7. The B osch D S C II system is an enhancem ent to the existing A S C + T5 system already in use. The D S C IIsystem is identicalto A S C + T5 w ith the addition ofthe steering an gle sensor and the D S C co ntrolunit.
4 Introduc tion to D S C
Dynamic Stability Control (DSC II) D ynam ic S tab ility C ontrol II (D S C II) is a further developm ent to the A B S /A S C + T5 traction co ntrolsystem . D S C I w as introduced in other m arkets on the E 32 and E 31 vehicles w ith the M 70 eng ine. The D S C system is d esigned to im prove the lateralstability of the vehicle in alldriving situations. W hereby A S C + T is p rim arily d esigned for longitudinal stability and providing the optim um traction for driving off, D S C adds lateralstability controlto the already proven system . For an y given turning angle and sp eed of the vehicle, there is a set difference betw een the rotationalsp eeds of the front w heels. If the rotationalsp eeds of the front w heels vary from this set difference, it m eans the vehicle is understeering or oversteering through the turn. This could lead to an unstable condition and possible loss of control. The D S C system is designed to m onitor this rotationaldifferen ce an d react to an y changes or deviations that m ight possibly occur. The D S C provides A S C controlfor the vehicle w hile driving through co rners o r any tim e the vehicle is not m oving straight ahead. In essence, the A S C + T5 becom es a D ynam ic S tab ility C ontrolS ystem w ith this ad ded feature.
5 Introd uc tion to D S C
DSC II
KL 30
ECM MAIN RELAY
ASC+T LAMP
ABS LAMP KL 15
POWER SUPPLY
SOLENOID RELAY
ASC SWITCH GROUND CONTROL POWER SUPPLY LF
ABS PUMP RELAY
GROUND CONTROL WHEEL
RF SPEED LR
INLET (4X) SENSORS
RR
ASC +T 5 / DSC
ASC+T/ DSC HYDRAULIC UNIT
OUTLET (4X) INTAKE PLUNGER
WHEEL SPEED X 4 AGS
PARK BRAKE SWITCH
ABS PUMP RELAY
6 Introduc tion to D S C
DIAGNOSIS
Bosch 5. 3 DSC III I-P-O
7 Introd uc tion to D S C
DSC III (Bosch 5.7) IPO
8 Introduc tion to D S C
DSC III 5.3 Components The B osch D S C III5.3 S ystem consists of the follow ing com ponents: • D C III C ontrol M od ule 8 3 P in • W heel S peed S ensors (A ctive H allEffect) • H ydraulic P ressure S enso r • S teering A ngle S ensor • R otation R ate (Yaw S ensor) • Lateral A cceleration S ensor • D S C S w itch • H and B rake S w itch • B rake S w itch • P re-C harging P um p • H ydraulic U nit • C harging P iston (750iL o nly)
BOSCH DSC III 5.7 COMPONENTS W ith the exception of the follow ing, allco m ponents of the D S C - 5.3 are carried over and their functionaloperation rem ains the sam e. • C ontrolM odule/H ydrau lic U nit - C ontrolM odule and hydraulic unit have been co m bined into one assem bly. The unit now includes the hydrau lic unit, co ntrol m od ule and return p um p. • R otational R ate/Lateral A cceleration S ensor - These tw o sensors have been com bined into one housing located under the driver’ s seat (under carpet). • B rake P ressure S ensor - The brake p ressu re sensor is installed in the hydraulic u nit housing. This p erform s the sam e function as the p revious hydraulic pressure sensor. 9 Introd uc tion to D S C
Control Module/ Hydraulic Unit The controlm odule used on the D S C IIIsystem s varies betw een m od els. The D S C III 5.3 system uses the sam e control m odule co nfiguration at the A S C + T5 system . The co ntrolm odule is an 83 pin unit located in the E-box. The D S C III5.7 system integ rates the co ntrol m odule into the hydrau lic unit. This reduces the size and w iring req uired for D S C operation. A dditionally the m otor relay and valve relay have been replaced by so lid state final stages in the controlm odule.
83 Pin Control Module Bosch DSC III 5.3
O n E39 an d E39 ap plications, the co ntrol m odule/hydraulic unit is located ah ead of the passenger side strut tow er. The hydraulic unit contains the follow ing com ponents: • Tw o p re-charge solenoid valves • Tw o changeo ver solenoid valves • Four intake so lenoid valves • Four outlet so lenoid valves • O ne return pum p
Control Module/Hydraulic Unit Bosch DSC III 5.7
10 Introduc tion to D S C
Wheel Speed Sensors The w heel speed sensors used are the sam e as on p revious E3 8 and E 39 m od els. The sensor is a hall effect type w hich sends a digital sq uare w ave to the D S C co ntrol unit. U nique to this sensor is the tw o w ire versus three w ire configuration as o n m ost halleffect circuits. The tw o w ire halleffect w heel sp eed sensors receive a stabilized 8 volt pow er supply from the controlm odule through one w ire. The ground path for the sensor is through the second w ire b ack to the controlm odule. The signalis generated by a pulse w heelaffecting the voltage flow through the hallelem ent in the sensor. The p ulse w heel is integrated into the w heel bearing assem bly, behind the seal. This p rotects the trigger w heelfrom foreign substances w hich m ay affect the w heel sp eed signal. This creates a sq uare w ave signalw ith a low of .75 volts and a h igh of 2.5 volts.
DSC Control Module
11 Introd uc tion to D S C
Hydraulic Pressure Sensor (Brake Pressure) The hydraulic system pressure sensor provides a 0-5 volt linear voltage signalto the D S C IIIcontrolm odule. The linear voltage is a proportionate indication of how hard the driver is pressing on the brake p edal. The signalis p rovided as an ad ditionaldeterm ining factor for the D S C III control m odule to m onitor the hydraulic p ressure p resent during all phases of operation, including: • N o B raking
• P artialB raking
• N ear A B S regulation state.
The sensor has three pins, pow er, ground and the 0 -5 volt signal. The sensor is capab le of m onitoring pressure from 0-250bar. The sensor is located in the front brake hydraulic circuit., the actuallocation varies by the follow ing application: • D S C III5.3 (740i/iL and 540i)- The brake pressu re sensor is located in the ch arge pum p assem bly. • D S C III 5.3 (750iL) - The sensor is located on the charge p iston u nit. • D S C III 5.7 (A LL) - The sensor is located on the h ydraulic u nit.
Pressure Sensor
Print
Change
End
Se
Pressure Sensor BMW Coding/programming SEL
1 2 3 4 5 6 Brake Pressure Sensor Location Bosch DSC III 5.3 (740i/iL, 540i)
12 Introduc tion to D S C
CAR MEMORY KEY MEMORY ZCS CODING PROGRAMMING ALIGNMENT EWSALIGNMENT EWS-
Brake Pressure Sensor Location Bosch DSC III 5.7 (All)
Steering Angle Sensor The steering an gle sensor is m ounted at the bottom of the steering co lum n near the flexible coupling. The sensor is a new type w hich differs from the D S C II system . This sensor is eq uipped w ith a p rocessor and is directly linked to the C A N bus to com m unicate w ith the D S C m odule. The sensor also co ntains the E D C IIIsteering angle sensor in the sam e housing but it is not on the C A N bus and the signal output to the E D C III co ntrolunit rem ains unchanged . The sensor stillutilizes tw o potentiom eters to determ ine the steering angle and the rate of steering angle change. These are the raw signals the C A N bus m icroprocesso r utilizes to create the steering an gle signal for broad cast over the C A N bus. A s w ith D S C II, this senso r still requires calibration after repairs to the steering or susp ension system . O nce the calibration is co m pleted, the sensor now also sends as identification num ber over the C A N bus to the D S C III m odule. The ID provides confirm ation is the D S C m odule that the steering angle sensor is p roperly calibrated . If the ID differs d ue to com ponent sw apping, it w illnot be p ossible to enter the D S C system for diagnosis. The D iagnosis P rogram w ill request that the steering angle sensor be recalibrated using “ S ervice Functions” . O nce co m plete, a new ID num ber is generated and the D S C m odule and steering angle senso r are p roperly m ated . The D S C III logic checks the plausibility of the steering angle sensor against other D S C III inputs (front w heel sp eeds, rotation rate and lateral acceleration senso rs). If the battery voltage is interrupted , the current steering w heelrotation is recalculated by the D S C m odule evaluating front w heel sp eeds.
13 Introd uc tion to D S C
Rotation Rate Sensor (Bosch 5.3) The new sensor is a m ajor co ntributor of the expanded capab ilities o fD S C III. W hen the rotation rate sensor w as introduced w ith D S C III 5.3, the sen sor w as a stand alone sensor located under the d rivers seat. O n D S C III 5.7, the sensor is now a com bined sensor w hich also h ouses the lateralacceleration sensor. To access the sensor, the seat m ust be rem oved, the door jam b interior trim pulled out of the w ay and the carpet rolled back. A sound insulating foam shell covers the sensor, this too m ust be p ulled upw ard off of the senso r prior to rem oval.
5 Pin Plug
Mounting Nuts
Sensor Operation The sensor is a sealed , self contained m icroprocessor that m onitors the vehicle’ s rate of rotationalacceleration on it’ s vertical axis. This is referred to as the “ yaw ”angle. The senso r contains an internal oscillating cylinder w hich is excited by various p iezo elem ents to an oscillation frequency o f 14K H z. This puts the cylinder in a free floating neutralstate. (zero point) W hen driving, the cylinder is deflected (rotated)by the effect ofthe forces from the vehicle cornering - this p roduces the torsional“ tw ist”on the cylinder. The senso r counteracts the “ tw ist”of the cylinder by increasing the pulse freq uency ofthe piezo elem ents to deflect the cylinder back to it’ s zero point.
Components are not serviceable. Photos are for reference only.
The pulse freq uency increase in m easured and rep resent the real tim e vehicle rotation rate. B ased on the m easurem ent, the sensor produces a linear D C voltag e that the D S C IIIco ntrolm odule uses to determ ine yaw angle.
14 Introduc tion to D S C
Oscillating Cylinder
Rotation Rate Sensor Signals The D S C IIIco ntrolm odule provides the rotation rate sensor w ith 12 volts o perating pow er and ground. In return, the sensor provides: • A standing 2.5 volt reference voltage signal(pin 4 of sensor) • A linear voltage signalran ging from 0.7 to 4.3 volts (pin 3 of sensor) The linear voltage equates to a range o f -50O (.7V ) to + 50O (4.3V) vehicle rotation rate change per second. The D S C III co ntrolm odule m onitors the signalvoltag e every 20m s.
D S C I I I
In conjunction w ith the steering angle, front w heel sp eeds and lateral forces, the rotation rate signal provides confirm ation of a vehicle p ushing the lim its of acceptable yaw . The D S C IIIcontrolm odule then regulates the torque o utput of the vehicle and m anipulates the brake system hydraulics as needed to co rrect for the under/oversteer co ndition. For continual plausibility testing, the D S C control m odule send a p redeterm ined test voltage signalto the rotation rate sensor (pin 5 of sensor). The sensor calculates the voltage value and sends feedback to the D S C III control m odule o ver the signal line (pin 2) every other 20m s signal cycle. If the feedback is out of plausible ran ge the D S C IIIm odule sets a fault. The D S C III m odule also checks the actual signal for plausibility by com paring it to com bined signals from the front w heelsp eed sensors, lateralacceleration sensor and the steering angle signalfrom the C A N bus. S ensor R eplacem ent If the rotation rate sensor is replaced, the new sensor m ust be calibrated w ith the D S C III co ntrol m odule through the S ervice Fun ction M enu of the D iag no sis program using the D IS plus or G T-1. 15 Introd uc tion to D S C
Lateral Acceleration Sensor (Bosch 5.3) This new sensor is a m ajor co ntributor of the expanded capabilities o f D S C III. It is located under the d rivers seat but m ounted on the vertical surface o f the inner rocker sill. (approxim ately 2”in front of the B pillar). The drivers seat and doo r jam b trim m ust be rem oved and the floor coverings p ulled out of the w ay to access the lateralacceleration senso r. S ensor O peration The lateralacceleration sensor is connected to the D S C III 1- Floor Covering 2 - 3 Pin Plug co ntrolm odule b y a 3 pin p lug. The sensor receives oper-2 - Mounting Screws ating pow er and ground. It return, it provides a linear voltage signalw hich is a m easurem ent of “ side to side”G -force acceleration. • The voltag e range is from 0.5 to 4.5 volts w hich co rresp ond s to a G force range of -1.5 to + 3.5 g. • W ith the vehicle stationary o n a levelsurface, approxim ately 1 .7 volts is present on the signalline. This is indicative of the nom inalvalue o f 0.0g. The senso r is a capacitive typ e senso r. U nder the effects of lateralacceleration, a m oving capacitor plate m oves in relation to a fixed capacitor plate. The result is a signal proportionalto the effect of lateralacceleration. The signalprovides additionalinform ation w hich enables the D S C IIIlogic a higher level of sensing the vehicles handling characteristics. The D S C reg ulation is calculated from : • The steering input from the desired vehicle direction from the driver • The R otation R ate sensor to determ ine the “ yaw ”of the veh icle • The left and right front w heelsp eed to verify the turning rate in the corner These inputs allow the D S C logic to calcu late the under/over steer w hile co rnering, an d the rate o f the vehicle speed entering the corner. For this calculation, the D S C can then com pensate by reducing engine torque, an d applying the appropriate braking to stabilize the vehicle for safer handling. 16 Introduc tion to D S C
Combined Rotation Rate/Lateral Acceleration Sensor (Bosch DSC III 5.7) O n D S C III (B osch 5.7) the R otation R ate sensor and the Lateral A cceleration sensor have been com bined into one unit. The sensor is located under the d river’ s seat and it is sm aller in size and w eight and is iso lated from chassis vibrations through it’ s rubber m ounting. The sensor provides the sam e inform ation as the tw o sp earate sensors used on D S C 5.3. It receives the sam e pow er and ground from the D S C controlm odule. For rotationalsp eed, the senso r produces a refernece signalof 2.5 volts and a linear voltage from 0.7 to 4.3 volts. This linear voltage input signalis used by the D S C controlm odule as the degree of rotationalrate (yaw ). The sensor also produces a linear voltag e signal from 0.5 to 4.5 volts. The D S C co ntrol m odule used this input to determ ine the side forces acting on the veh icle for D S C reg ulation
17 Introd uc tion to D S C
DSC Switch The system is active w henever the ignition is sw itched on. W hen pressed, the sw itch p rovides a m om entary 12 volt signal to the D S C co ntrolm odule to sw itch the system off. The D S c indictator in the cluster w ill be illum inated to indicate that the system is off. W hen p ressed ag ain, the system sw itches b ack on and the D S C ind icator goes o ff.
Handbrake Switch The hand brake sw itch is a g round input the D S C m od ule. M S R regulation is cancelled w hen there is a “ H andbrake O n”signalpresent.
Brake Switch The b rake sw itch is used to activate the A B S functions in the D S C III m odule. If the system receives a brake sw itch signal w hen in A S C m ode and reg ulating, A S C reg ulation is cancelled. The A B S reg ulating phase is also cancelled w hen the brake sw itch signal is not present.
18 Introduc tion to D S C
DSC III (BOSCH 5.3) Hydraulic System Components A s m entioned at the beginning of this section, there are m inor differences in the hydraulics for the 750iL com pared w ith the 740i/iL and 540iA .The follow ing co m ponents are the sam e for either variation of the system :
Hydraulic Unit:
VALVE SOLENOIDS
• S im ilar to D S C II hydraulic unit • M od ulates brake pressure during A B S , C B C , A S C and D S C control procedure. • C ontains: - 1 p um p m otor, - 2 return reciprocating pum ps - 2 p reload valves, - 2 changeover valves - 2 accum ulator cham bers - 2 d am per cham bers - 4 inlet valves - 4 outlet valves
PUMP MOTOR
Master Cylinder: M aster cylinder, fluid reservo ir and level sw itch. A ll new com ponents.
CHANGEOVER VALVE
PRELOAD VALVE
CHANGEOVER VALVE
PRELOAD VALVE
PUMP
INLET VALVE
LEFT REAR BRAKE
OUTLET VALVE
PUMP
OUTLET VALVE
RIGHT REAR BRAKE
INLET VALVE
INLET VALVE
OUTLET VALVE
LEFT FRONT BRAKE
OUTLET VALVE
INLET VALVE
RIGHT FRONT BRAKE
19 Introd uc tion to D S C
To ensure sufficient brake fluid supply is alw ays available to the hydraulic unit during A S C / D S C hydraulic reg ulation, the system req uires an additional pum ping system not eq uipped on any previous A S C + T system . The pum ping system s are d ifferent on the 750iL com pared w ith the 740i/iL & 540iA and are as follow s: • 740i/iL & 540iA = Charge pump - located next to the m aster cylinder. • 750iL = Pre-boost pump and separate charge piston. These com ponents are also m ounted next to the brake fluid m aster cylinder and fluid reservoir.
CHANGEOVER VALVE
PRELOAD VALVE
CHANGEOVER VALVE
PRELOAD VALVE
PUMP
INLET VALVE
LEFT REAR BRAKE
20 Introduc tion to D S C
OUTLET VALVE
PUMP
OUTLET VALVE
RIGHT REAR BRAKE
INLET VALVE
INLET VALVE
OUTLET VALVE
LEFT FRONT BRAKE
OUTLET VALVE
INLET VALVE
RIGHT FRONT BRAKE
Hydraulic Charge E xisting A S C + T and D S C IIsystem s already perform hydraulic controlreg ulation b ut do not req uire the ad ditionalcharge p um p system s. W hy? The reason b eing tho se system s only actuate the rear axle circuits. O bviously, the D S C III system has the capability to actuate front and rear axle circuits together w hich requires additionalhyd raulic fluid supply. For this reason, during an ASC or DSC regulation function requiring hyd raulic intervention, the D S C IIIcontrolm odule sw itches the electricalcharge pum p on to provide this additionalfluid.
740i/iL & 540iA Vehicles: W hen activated , the C harge P um p delivers a brake pressu re of10 - 15 bar to the front axle circuit of the hyd raulic unit and into the front axle circuit pressure cham ber of of the m aster cylinder. The m aster cylinder piston for the front axle circuit contains a notched restrictor forw ard of the central valve w hich allow s excess fluid to return to the reservoir under a restriction. The pressurized fluid also acts o n the rear axle circuit of the m aster cylinder. This p rovides the hyd raulic charge to the rear axle circuit of the hyd raulic unit as needed.
21 Introd uc tion to D S C
750iL Vehicles: The electric Pre-boost pump delivers a brake fluid pressure of 7-15 bar to the iso lated cham ber of the charge piston. The pre-boost pum p inco rporates an integ ral pressure relief valve w hich opens at 15 bar. From the iso lated cham ber the fluid returns to the reservoir through a restriction. The restriction causes p ressure to build in the cham ber w hich pushes the pistons o utw ard. This im m ediately acts on tw o valves w hich block the norm al braking circuits that flow through the charge piston ports. The pressu re in the isolated cham ber co ntinues to push the pistons outw ard delivering the required charge p ressure.
CHARGE PISTON
PRE-BOOST PUMP
For A B S and C B C op eration, the p um p system s are not sw itched on, only during A S C /D S C reg ulation req uiring hydraulic intervention are the pre-boost pum p or the charge pum p sw itched on. The balance o f the hydraulic system fun ctions op erate in the sam e fam iliar m anor of all previous system s. The individual brake circuits can be iso lated as needed to restore laterallocating forces through pressure build, hold and release phases o f operation. D uring an A S C hydraulic intervention requiring only rear w heelbrake application, the inlet valves for the front w heels are closed preventing any p ressure influence from the charge pum p system s. 22 Introduc tion to D S C
CHANGEOVER VALVE
PRELOAD VALVE
CHANGEOVER VALVE
PRELOAD VALVE
PUMP
INLET VALVE
LEFT REAR BRAKE
OUTLET VALVE
PUMP
OUTLET VALVE
RIGHT REAR BRAKE
INLET VALVE
INLET VALVE
OUTLET VALVE
LEFT FRONT BRAKE
OUTLET VALVE
INLET VALVE
RIGHT FRONT BRAKE
23 Introd uc tion to D S C
Principle of Operation Dynamic Stability Control Systems Introduction D ynam ic S tab ility C ontrol(D S C IIIversion 5.3)w as introduced on the 1 998 M odelYear E 38 and E39 - 540 vehicles. Fo r M odelYear 1999, the system is enhanced w ith additionalco ntrolfunctions and a new com bined rotationalrate/lateralacceleration senso r as version 5.7. It co ntinu es to b e offered as standard eq uipm ent in the E 38 and E39 - 540 m odels. The new functions are titled as the D ynam ic B raking S ystem and include the: •D ynam ic B rake C ontrol (D B C ) •M axim um B rake C ontrol (M B C ) D S C III adds a further dim ension to the d ynam ic stab ility co ntrolsystem . D S C II has the ability to m ildly correct for lateralinstability and only at the rear brakes w hen braking controlis necessary. D S C IIIhas the ability to brake any w heel during cornering m aneuvers w here the controlm odule’ s p rogram m ed lim its for vehicle o versteer an d understeer are exceeded. N ew sensors are ad ded to the D S C III system to m onitor the rotational rate of the veh icle around its verticalaxis and a lateralacceleration senso r to m onitor the side to side forces on the vehicle. The hydraulic system of the D S C IIhas also been m odified to allow brake reg ulation on the front w heels and to ensure that the supply of brake fluid for D S C II regulation is m aintained. Tw o different hyd raulic system s are used on the B osch 5.3 D S C system as follow s: • 740i/iL & 540iA use a charge p um p for the front brake circuit. • 750iL uses a boost pum p and sep arate charge p iston for both the front and rear brake circuits. The hydraulic system used on the B osch D S C III 5.7 has chang ed on the E 38 and E39 . The 750iL now uses a sim ilar hydraulic system tothe 740i/iL and 540i. The charge p iston and pre-boost pum p have been elem inated . The brake pressure sensor is no w located in the hydraulic unit on allB osch 5.7 system s.
24 Introduc tion to D S C
Dynamic Stability Control (DSC III) A ll of the fam iliar braking and straight line traction control features and system com m unication carry over from D S C II. B ased on select high/select low logic, the D S C III control m odule selects a vehicle stabilizing strategy b ased on the sp ecific input signal values it is m onitoring at the m om en t. For all D S C strateg ies this b egins w ith en gine intervention to red uce torque: • Fo r the 750iL this is hand led via C A N com m unication, D S C III to EM L to m inim ize the throttle angle of the D K m otors (750iL). For the 740i/iL and 540iA this is handled by d irect D S C III activation of the A D S II throttle housing. • If ad ditional torque red uction is necessary, D S C IIIinform s D M E over C A N to: a. R etard ignition tim ing b. S hut dow n the fuelinjection to individualcylinders D S C III m onitors under/oversteer co nditions through the follow ing co m ponents: • The driver’ s d esired steering angle - steering angle signal over C A N bus. • Vehicle sp eed an d speed differential at front w heels - w heelspeed sensors • D ynam ic forces o f lateralacceleration and yaw placed on the vehicle. This is possible w ith these tw o new co m ponents. The results are as follow s:
25 Introd uc tion to D S C
The exp anded hydraulic control of individual w heel circuits is apparent w hen stabilizing a vehicle exhibiting an oversteer condition as follow s:
Transm ission system intervention also occurs d uring any A S C /D S C reg ulating phase. Through C A N bus co m m unication the A G S control m od ule is inform ed to d elay any gear ch anges d uring reg ulation. This prevents any unw an ted driveline dynam ic chan ges during D S C reg ulation. Though D S C III provides state of the art, electronic correction of undesirable vehicle handling characteristics, it is im portant to rem em ber vehicle stability is alw ays subject to the physical law s of centrifugal force and extrem e road conditions. Good judgement and
common sense on the part of the driver are still required.
26 Introduc tion to D S C
DSC Features Corner Braking Control (CBC) C B C is a feature of dynam ic stability controlthat is d esigned to im prove the vehicle’ s stability if the driver brakes w hile driving through a curve. If the vehicle is braked w hile driving through a curve, an uneq ual braking force w illbe ap plied to the w heels d ue to the w eight shift of the vehicle to the outside of the turn. B ased on the vehicle speed and the speed differentialof the tw o front w heelsp eed sensors, the controlm odule can determ ine if C B C needs to be activated w hen the d river applies the b rakes. If C B C is activated, the regulation w ill pulse the w heel brakes o n the outside of the vehicle to provide an equal braking force on allfour w heels.
Dynamic Braking System (DBS) The dynam ic b raking system is designed to enhance the braking co ntrolof the D S C for the driver of the vehicle. The d ynam ic b raking co ntrolan d m axim um braking co ntrolare functions that are p rogram m ed into the controlelectronics of the D S C w ith no ad ditionalhardw are chang es. The D ynam ic b raing system features consist of D B C and M B C .
Dynamic Braking Control (DBC) The D B C function is designed to provide the m axim um braking force availab le d uring rap id (panic) braking situations. The D S C co ntrolm odule looks at the inputs from the brake ped al sw itch and the signal from the brake pressu re sensor on the m aster cylinder. The criteria for activation of D B C is how rapidly is the brake pressure b uilt up w ith the brake pedal depressed. The total criteria required for D B C activation includes: •B rake sw itch O N •B rake pressure b uild up > threshold value •Veh icle road speed > 5M P H •Vehicle not in reverse •N ot allw heels in A B S regulation If the threshold for D B C activation is achieved, the D S C controlm odule w illactivate a p ressure b uild up regulation phase through the hyd raulic unit. The p ressure at all w heels is increased up to the A B S regulation point. This occurs even if the d river does not achieve the A B S regulation point w ith the p edal. The rear axle brakes are controlled w ith select-low regulation and the front axle brakes are controlled individually. A B S regulation w ill continue until the driver releases the pedal and the p ressure in the m aster cylinder drops below the threshold value stored in the D S C co ntrolm odule. 27 Introd uc tion to D S C
Maximum Brake Control The M B C function is also designed to en han ce a driver initiated braking procedure. The M B C w illbuild up the pressu re in the rear brake circuit w hen the front brakes are alread y in an A B S regulation cycle. The additionalbraking pressure at the rear w heels w illshorten the stopping distan ce. The follow ing criteria m ust be m et before the D S C co ntrol m odule w ill activate M B C : •B oth front w heelbrakes in A B S regulation •Vehicle speed > 5 M P H •Vehicle not in reverse •D B C and pressure sensor initialization test O K •R ear w heels not in A B S reg ulation
28 Introduc tion to D S C
Diagnosis The follow ing diagnostic functions are available using the D IS plus or G T-1. Control Unit Functions: E xpert m ode d iag no sis availab le at an y tim e d uring troubleshooting. To enter: press the C ontrol U nit Functions b utton at the right low er corner of the screen. The co ntents are: Identification • Delete Fault Memory • Read Fault Memory • Component Activation • Status queries (requests)
Service Functions: P rovides access to sp ecialized test m odules used as post rep air procedures. To en ter: • Function S election • S ervice Function s • C h assis • D ynam ic S tab ility C ontrol Th e contents are: • Connection Speed Sensor: A test to verify the p roper w iring to the w heel speed senso rs • Connection Brake Lines: A test to verify the p roper brake p ipe connections to the hyd raulic unit. • Adjustment Functions: Test m od ules to initialize certain com ponents a fter rep air w ork is p erform ed • S teering A ngle S ensor • LateralA cceleration S ensor • P ressure S ensors
Test Modules: Faults w ith the D S C III system can be d iag no sed using fault or sym ptom driven test m od ules. To beg in diag no sis: • Perform the Quick Test. • Select Vehicle Symptom from the Symptom Selection page. • Select Test Module from Test Plan page. • Press the Test Schedule Button.
29 Introd uc tion to D S C
Coding
Print
C oding m ust be perform ed after rep lacem ent of the D S C III co ntrol m odule o r the steering ang le sen sor. ZC S co ding is found in the C oding and P rogram m ing selection from the start screen or w hen pressing the C han ge button. Follow on-screen instructions for initialization of com ponents after co m pleting the co ding p rocess.
Change
End
Services
BMW Coding/programming SELECTION
1 2 3 4 5 6
CAR MEMORY KEYMEMORY ZCS CODING PROGRAMMING ALIGNMENT EWS-DME ALIGNMENT EWS-DDE
Note
Adjustment Functions A djustm ent (initialization) is required w hen: • R ep lacing the D S C III C ontrolU nit. • R ep lacing /R e-coding the S teering A ng le S ensor. • R ep lacing one or both B rake P ressure S ensors. • R ep lacing Lateral A cceleration S ensor.
Steering Angle Sensor The steering angle sensor req uires an offset ad justm ent after the sensor has been rep laced , coded or after repairs to the steering or susp ension system . The offset adjustm ent inform s the steering angle senso r processor of the straight ahead position of the front w heels. The ad justm ent is perform ed by co m pleting the Test M odule found in S ervice Fun ctions. O nce the adjustm ent is co m plete the sensor sends an identification nu m ber over the C A N bus to the D S C controlunit. The ID provides confirm ation that the steering angle sensor is co ded and has successfully com pleted the ad justm ent procedure.
Special Tools S pecialTools available for the D S C III system consist of: Tool #
Description
Purpose
34 5 240
42 P in V-C a b le
For B .O.B . 61 4 390
61 4 390
60 P in B .O.B .
For pin by pin diagnosis
34 5 160
P res s ure S ens or S oc ket
For ins ta lla tion a nd remova l of hyd ra ulic bra ke pres sure s enso r.
61 4 420
83 P in B .O.B .
For pin b y pin d ia g no s is of B os c h DS C III 5.3 and AS C + T5
30 Introd uc tion to D S C
Review Questions 1. W hat are the prim ary differences b etw een B osch 5.3 and 5.7?
2. W hat is the nom inal voltag e output of the R otation R ate sensor w hen the vehicle is at rest?
3. W hat type o f w heel speed sensors are used on the B osch D S C III system on the E 38 and E39?
4. List the required activation criteria for D B C activation:
5. List the required activation criteria for M B C activation:
31 Introd uc tion to D S C