Table of Contents Introduction to DSC Subject Page Module Objectives.2 Overview of DSC Systems.3 Puspose of the System.4 DSC Components.9 Control Module/Hydraulic Unit.10 Wheel Speed Sensors.11 Hydraulic Pressure Sensor.12 Steering Angle Sensor.13 Rotation Rate Sensor.14 Lateral Acceleration Sensor.16 Combined Rotation Rate/Lateral Acceleration Sensor.17 DSC Switch.18 Handbrake Switch.18 Brake Switch.18 Hydraulic System Components.19 Principle of Operation.24 Diagnosis.29 Review Questions.31 1 Introduction to DSC Model: 1995-1997 E38 750iL, E31 850Ci 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: All E38 and E39 with Bosch 5.7 DSC III Objectives: After completion of this module you should be able to: Understand Basic DSC operation. • Identify Components within the DSC System (DSC 5.3 and DSC 5.7). • Locate Components within the DSC system. • Understand the differences between ASC and DSC. • Understand Differences between Bosch DSC 5.7 and 5.3. 2 Introduction to DSC Overview of DSC Systems Model Year E36 E36/7 Z3 E46 E39 E38 E53 E52 E65 E66 E85 1998 ASC+T ASC +T MK IV G N/A 9/97 ASC +T5 S: 528i DSC III 5.3 S: 540i N/A 528i 9/97 DSC III Bosch 5.3 S: 740i/iL S: 750iL N/A N/A N/A N/A 1999 ASC +T MK IV G 328iC 318ti ASC +T MK 20 El (Except M) ASC +T Mk IV G (M Versions) ASC Teves MK 20 El 9/98 ASC +T5 S: 528i Bosch DSC III 5.7 S: 540i O: 528i 3/98 Bosch DSC III 5.7 S: 740i/iL S: 750iL N/A N/A N/A N/A 2000 N/A from 4/99 Teves MK 20 DSC III DSC III Teves MK 20 El from 6/99 6/99 Bosch DSC III 5.7 STD All 3/99 Bosch DSC III 5.7 STD All DSC III Bosch 5.7 9/99 DSC III Bosch 5.7 1/00 N/A N/A 2001 N/A From 9/00 Teves MK 60 DSC III M Versions Teves MK 20 DSC III DSC III Teves MK 60 from 9/00 M3 Teves MK 20 E46/16 AWD Bosch DSC III 5.7 DSC III Bosch 5.7 DSC III Bosch 5.7 DSC III Bosch 5.7 DSC III Bosch 5.7 N/A N/A 2002 N/A Same as 2001 DSC III Bosch 5.7 N/A DSC III Bosch 5.7 ■ N/A 2003 N/A N/A Same as 2001 DSC III Bosch 5.7 N/A DSC III Bosch 5.7 DSC III Bosch 5.7 ■ DSC III Teves MK60 S = STANDARD EQUIPMENT 0 = OPTIONAL EQUIPMENT STD All = Standard All Models 3 Introduction to DSC Dynamic Stability Control (DSC ll/DSC III) Purpose of the System DSC adds a further dimension to the traction control system. DSC adds lateral control to this already proven system. The traction control system was designed for longitudinal stability and providing the optimum traction for driving off. DSC II has the ability to mildly correct for lateral instability and only at the rear brakes when braking control is necessary. DSC III has the ability to brake any wheel during cornering maneuvers where the control module's programmed limits for vehicle oversteer and understeer are exceeded. The DSC II system monitors the input values from the two front wheel speed sensors and the steering angle sensor. The rotational speeds of the front wheels for the given turning angle are compared to the programmed values in the DSC control module. If the values are outside the programmed limits, DSC regulation will be activated. New sensors are added to the DSC III system to monitor the rotational rate of the vehicle around its vertical axis and a lateral acceleration sensor to monitor the side to side forces on the vehicle. On DSC II or DSC III systems, the control regulation follows the same outputs as for trac¬ tion control regulation with: Throttle valve regulation Engine intervention Rear brake control The control phases are brief and only occur long enough to correct the unstable condition. The following text in this training manual will focus on Bosch DSC III 5.3 and 5.7. The Bosch DSC II system is an enhancement to the existing ASC+T5 system already in use. The DSC II system is identical to ASC+T5 with the addition of the steering angle sensorand the DSC control unit. 4 Introduction to DSC Dynamic Stability Control (DSC II) Dynamic Stability Control II (DSC II) is a further development to the ABS/ASC+T5 traction control system. DSC I was introduced in other markets on the E32 and E31 vehicles with the M 70 engine. The DSC system is designed to improve the lateral stability of the vehicle in all driving situ¬ ations. Whereby ASC+T is primarily designed for longitudinal stability and providing the optimum traction for driving off, DSC adds lateral stability control to the already proven sys¬ tem. For any given turning angle and speed of the vehicle, there is a set difference between the rotational speeds of the front wheels. If the rotational speeds of the front wheels vary from this set difference, it means the vehicle is understeering or oversteering through the turn. This could lead to an unstable condition and possible loss of control. The DSC system is designed to monitor this rotational difference and react to any changes or deviations that might possibly occur. The DSC provides ASC control forthe vehicle while driving through corners or any time the vehicle is not moving straight ahead. In essence, the ASC+T5 becomes a Dynamic Stability Control System with this added fea¬ ture. OUTSIDE WHEEL ROTATES FASTER 5 Introduction to DSC DSC II KL 15 6 Introduction to DSC Bosch 5. 3 DSC III l-P-0 ECM MAIN RELAY KL 30 KL 15 siiC DSC SWITCH — O TvAT .'.L LF /^S n n n RF LR RR ■—U 1- 1 WHEEL «=□ 1 FLrUn I 1 ' SPEED 1 rL ^ , 1 1 SENSORS i CHARGE PRESSURE SENSOR REFERENCE VOLTAGE SIGNAL VOLTAGE ROTATION RATE SENSOR - + SIGNAL VOLTAGE LATERAL ACCELERATION SENSOR 1 ELECTRONIC BRAKE LIGHT SWITCH j TO LCM PARK BRAKE SWITCH ABS PUMP RELAY DSC KL 15 POWER SUPPLY GROUND CONTROL POWER SUPPLY GROUND CONTROL SOLENOID RELAY PUMP ABS PUMP RELAY INLET (4X) OUTLET (4X) CHANGEOVER (2x) PRE-LOAD (2x) HJ — 'iiir mmj— DSCIII HYDRAULIC UNIT POWER SUPPLY GROUND SENSOR TEST 740i/iL & 540iA = CHARGE PUMP CONTROL 750iL = PRE-BOOST PUMP CONTROL I ROTATION RATE SENSOR STEERING ANGLE SENSOR WITH INTEGRAL MICRO¬ PROCESSOR WHEEL SPEED X4 EDO DIAGNOSIS DME II IKE & DME I 7 Introduction to DSC DSC III (Bosch 5.7) IPO ECM MAIN RELAY IM KL 30 KL 15 DSC SWITCH RF LR ■-u i 1 WHEEL «=□ 1 1 1 ' SPEED =0 1 , 1 1 SENSORS i arm BRAKE PRESSURE SENSOR REFERENCE VOLTAGE SIGNAL VOLTAGE SIGNAL VOLTAGE ROTATION RATE SENSOR ELECTRONIC BRAKE LIGHT SWITCH i TOLCM PARK BRAKE SWITCH DSC KL 15 POWER SUPPLY POWER SUPPLY PUMP INLET (4X) OUTLET (4X) CHANGEOVER (2x) PRE-LOAD (2x) W&T' "IfiQMT W&T' ■ mrnr - 1 DSCIII HYDRAULIC UNIT POWER SUPPLY GROUND SENSOR TEST ROTATION RATE SENSOR CHARGE PUMP CONTROL 1 io ► | o 1 STEERING ANGLE SENSOR WITH INTEGRAL MICRO¬ WHEEL SPEED X 4 EDO ■t DIAGNOSIS DMEII IKE & DME 8 Introduction to DSC DSC III 5.3 Components The Bosch DSC III 5.3 System consists of the following components: DC III Control Module 83 Pin Wheel Speed Sensors (Active Hall Effect) Hydraulic Pressure Sensor Steering Angle Sensor Rotation Rate (Yaw Sensor) Lateral Acceleration Sensor DSC Switch Hand Brake Switch Brake Switch Pre-Charging Pump Hydraulic Unit Charging Piston (750iL only) Bosch DSC III 5.7 Components With the exception of the following, all components of the DSC - 5.3 are carried over and their functional operation remains the same. Control Module/Hydraulic Unit - Control Module and hydraulic unit have been combined into one assembly. The unit now includes the hydraulic unit, control module and return pump. Rotational Rate/Lateral Acceleration Sensor - These two sensors have been combined into one housing located under the driver's seat (under carpet). Brake Pressure Sensor - The brake pressure sensor is installed in the hydraulic unit housing. This performs the same function as the previous hydraulic pressure sensor. 9 Introduction to DSC Control Module/ Hydraulic Unit The control module used on the DSC III sys¬ tems varies between models. The DSC III 5.3 system uses the same control module configuration at the ASC+T5 system. The control module is an 83 pin unit located in the E-box. The DSC III 5.7 system integrates the control module into the hydraulic unit. This reduces the size and wiring required for DSC opera¬ tion. Additionally the motor relay and valve relay have been replaced by solid state final stages in the control module. 83 Pin Control Module Bosch DSC III 5.3 On E39 and E39 applications, the control module/hydraulic unit is located ahead of the passenger side strut tower. The hydraulic unit contains the following components: Two pre-charge solenoid valves Two changeover solenoid valves Four intake solenoid valves Four outlet solenoid valves One return pump Introduction to DSC Wheel Speed Sensors The wheel speed sensors used are the same as on previous E38 and E39 models. The sensor is a hall effect type which sends a digital square wave to the DSC control unit. Unique to this sensor is the two wire versus three wire configuration as on most hall effect circuits. The two wire hall effect wheel speed sensors receive a stabilized 8 volt power supply from the control module through one wire. The ground path for the sensor is through the sec¬ ond wire back to the control module. The signal is generated by a pulse wheel affecting the voltage flow through the hall element in the sensor. The pulse wheel is integrated into the wheel bearing assembly behind the seal. This protects the trigger wheel from foreign substances which may affect the wheel speed signal. This creates a square wave signal with a low of .75 volts and a high of 2.5 volts. DSC Control Module Introduction to DSC Hydraulic Pressure Sensor (Brake Pressure) The hydraulic system pressure sensor provides a 0-5 volt linear voltage signal to the DSC III control module. The linear voltage is a proportionate indication of how hard the driver is pressing on the brake pedal. The signal is provided as an additional determining factorfor the DSC III control module to monitor the hydraulic pressure present during all phases of operation, including: No Braking Partial Braking NearABS regulation state. The sensor has three pins, power, ground and the 0-5 volt signal. The sensor is capable of monitoring pressure from 0-250bar. The sensor is located in the front brake hydraulic circuit., the actual location varies by the following application: DSC III 5.3 (740i/iL and 540i) - The brake pressure sensor is located in the charge pump assembly. DSC III 5.3 (750iL) - The sensor is located on the charge piston unit. DSC III 5.7 (ALL) - The sensor is located on the hydraulic unit. Brake Pressure Sensor Location Bosch DSC III 5.3 (7401/IL, 540i) Brake Pressure Sensor Location Bosch DSC III 5.7 (All) Introduction to DSC Steering Angle Sensor The steering angle sensor is mounted at the bottom of the steering column near the flexi¬ ble coupling. The sensor is a new type which differs from the DSC II system. This sensor is equipped with a processor and is directly linked to the CAN bus to communicate with the DSC mod¬ ule. The sensor also contains the EDC III steering angle sensor in the same housing but it is not on the CAN bus and the signal output to the EDC III control unit remains unchanged. The sensor still utilizes two potentiometers to determine the steering angle and the rate of steering angle change. These are the raw signals the CAN bus microprocessor utilizes to create the steering angle signal for broadcast over the CAN bus. As with DSCII, this sensor still requires calibration after repairs to the steering or suspen¬ sion system. Once the calibration is completed, the sensor now also sends as identifica¬ tion number over the CAN bus to the DSC III module. The ID provides confirmation is the DSC module that the steering angle sensor is properly calibrated. If the ID differs due to component swapping, it will not be possible to enter the DSC sys¬ tem for diagnosis. The Diagnosis Program will request that the steering angle sensor be recalibrated using "Service Functions”. Once complete, a new ID number is generated and the DSC module and steering angle sensor are properly mated. The DSC III logic checks the plausibility of the steering angle sensor against other DSC III inputs (front wheel speeds, rotation rate and lateral acceleration sensors). If the batten/ voltage is interrupted, the current steering wheel rotation is recalculated by the DSC mod¬ ule evaluating front wheel speeds. CAN BUS MICROPROCESSOR Introduction to DSC Rotation Rate Sensor (Bosch 5.3) The new sensor is a major contributor of the expanded capabilities of DSC III. When the rotation rate sensor was introduced with DSC III 5.3, the sensor was a stand alone sensor located under the drivers seat. On DSC III 5.7, the sensor is now a combined sensor which also houses the lateral acceleration sensor. VERTICAL AXIS RATE OF CHANGE To access the sensor, the seat must be removed, the doorjamb interior trim pulled out of the way and the carpet rolled back. A sound insulating foam shell covers the sensor, this too must be pulled upward off of the sensor prior to removal. Sensor Operation The sensor is a sealed, self contained microprocessor that monitors the vehicle’s rate of rotational acceleration on it's vertical axis. This is referred to as the "yaw” angle. The sensor contains an internal oscillating cylinder which is excited by various piezo elements to an oscillation frequency of 14KHz. This puts the cylinder in a free floating neutral state, (zero point) When driving, the cylinder is deflected (rotated) by the effect of the forces from the vehicle cornering - this produces the tor¬ sional "twist" on the cylinder. The sensor counteracts the "twist" of the cylinder by increasing the pulse frequency of the piezo elements to deflect the cylinder back to it’s zero point. Components are not serviceable. Photos are for reference only. Oscillating Cylinder The pulse frequency increase in measured and represent the real time vehicle rotation rate. Based on the measurement, the sensor produces a linear DC voltage that the DSC III control module uses to determine yaw angle. Introduction to DSC Rotation Rate Sensor Signals The DSC III control module provides the rotation rate sensor with 12 volts operating power and ground. In return, the sensor provides: A standing 2.5 volt reference voltage signal (pin 4 of sensor) A linear voltage signal ranging from 0.7 to 4.3 volts (pin 3 of sensor) The linear voltage equates to a range of -50° (,7V) to +50° (4.3V) vehicle rotation rate change per second. The DSC III control module monitors the signal voltage even/ 20ms. VERTICAL AXIS c c REFERENCE VOLTAGE K K SIGNAL VOLTAGE SENSOR TEST SIGNAL ROTATION RATE SENSOR In conjunction with the steering angle, front wheel speeds and lateral forces, the rotation rate signal provides confirmation of a vehicle pushing the limits of acceptable yaw. The DSC III control module then regulates the torque output of the vehicle and manipulates the brake system hydraulics as needed to correct for the under/oversteer condition. For continual plausibility testing, the DSC control module send a predetermined test volt¬ age signal to the rotation rate sensor (pin 5 of sensor). The sensor calculates the voltage value and sends feedback to the DSC III control module over the signal line (pin 2) even/ other 20ms signal cycle. If the feedback is out of plausible range the DSC III module sets a fault. The DSC III module also checks the actual signal for plausibility by comparing it to com¬ bined signals from the front wheel speed sensors, lateral acceleration sensor and the steer¬ ing angle signal from the CAN bus. Sensor Replacement If the rotation rate sensor is replaced, the new sensor must be calibrated with the DSC III control module through the Service Function Menu of the Diagnosis program using the DIS plus or GT-1. 15 Introduction to DSC Lateral Acceleration Sensor (Bosch 5.3) This new sensor is a major contributor of the expanded capabilities of DSC III. It is located under the drivers seat but mounted on the ver¬ tical surface of the inner rocker sill, (approximately 2" front of the B pillar). The drivers seat and doorjamb trim must be removed and the floor coverings pulled out of the way to access the lat¬ eral acceleration sensor. Sensor Operation The lateral acceleration sensor is connected to the DSC control module by a 3 pin plug. The sensor receives oper¬ RATE OF CHANGE IN SIDE-TO-SIDE MOVEMENT (LATERAL ACCELERATION) 1- Floor Covering 2 - 3 Pin Plug 2 - Mounting Screws ating power and ground. It return, it provides a linear volt¬ age signal which is a measurement of "side to side" G-force acceleration. The voltage range is from 0.5 to 4.5 volts which corresponds to a G force range of -1.5 to +3.5 g. With the vehicle stationary on a level surface, approximately 1.7 volts is present on the signal line. This is indicative of the nominal value of O.Og. The sensor is a capacitive type sensor. Under the effects of lateral acceleration, a moving capacitor plate moves in relation to a fixed capacitor plate. The result is a signal propor¬ tional to the effect of lateral acceleration. The signal provides additional information which enables the DSC III logic a higher level of sensing the vehicles handling characteristics. The DSC regulation is calculated from: The steering input from the desired vehicle direction from the driver The Rotation Rate sensor to determine the "yaw” of the vehicle The left and right front wheel speed to verify the turning rate in the corner These inputs allow the DSC logic to calculate the under/over steer while cornering, and the rate of the vehicle speed entering the corner. For this calculation, the DSC can then com¬ pensate by reducing engine torque, and applying the appropriate braking to stabilize the vehicle for safer handling. Introduction to DSC Combined Rotation Rate/Lateral Acceleration Sensor (Bosch DSC III 5.7) On DSC III (Bosch 5.7) the Rotation Rate sensor and the Lateral Acceleration sensor have been combined into one unit. The sensor is located under the driver's seat and it is small¬ er in size and weight and is isolated from chassis vibrations through it's rubber mounting. The sensor provides the same information as the two spearate sensors used on DSC 5.3. It receives the same power and ground from the DSC control module. For rotational speed, the sensor produces a refernece signal of 2.5 volts and a linear volt¬ age from 0.7 to 4.3 volts. This linear voltage input signal is used by the DSC control mod¬ ule as the degree of rotational rate (yaw). The sensor also produces a linear voltage signal from 0.5 to 4.5 volts. The DSC control module used this input to determine the side forces acting on the vehicle for DSC regula¬ tion REFERENCE VOLTAGE SIGNAL VOLTAGE ACCELERATION SENSOR INPUT ROTATION RATE SENSOR/ ACCELERATION SENSOR o Introduction to DSC DSC Switch The system is active whenever the ignition is switched on. When pressed, the switch provides a momentary 12 volt signal to the DSC control module to switch the sys¬ tem off. The DSc indictator in the cluster will be illumi¬ nated to indicate that the system is off. When pressed again, the system switches back on and the DSC indi¬ cator goes off. Handbrake Switch The handbrake switch is a ground input the DSC module. MSR reg¬ ulation is cancelled when there is a "Handbrake On" signal present. Brake Switch The brake switch is used to activate the ABS functions in the DSC III module. If the system receives a brake switch signal when in ASC mode and regulating, ASC regulation is can¬ celled. The ABS regulating phase is also cancelled when the brake switch signal is not present. KL 15 Introduction to DSC DSC III (BOSCH 5.3) Hydraulic System Components As mentioned at the beginning of this section, there are minor differences in the hydraulics forthe 750iL compared with the 740i/iL and 540iA. The following components are the same for either variation of the system: Hydraulic Unit: Similar to DSC II hydraulic unit Modulates brake pressure during ABS, CBC, ASC and DSC control procedure. Contains: - 1 pump motor, - 2 return reciprocating pumps - 2 preload valves, - 2 changeover valves - 2 accumulator chambers - 2 damper chambers - 4 inlet valves - 4 outlet valves Master Cylinder: aster cylinder, fluid reser¬ voir and level switch. All new components. DSC III HYDRAULIC UNIT 0 0 •v V# •v JNLET OUTLET OUTLET INL VALVE VALVE VAIVF VA VALVE VALVE LEFT REAR BRAKE RIGHT REAR BRAKE , RIGHT '#•)) ) FRONT BRAKE Introduction to DSC To ensure sufficient brake fluid supply is always available to the hydraulic unit during ASC/ DSC hydraulic regulation, the system requires an additional pumping system not equipped on any previous ASC+T system. The pumping systems are different on the 750il_ compared with the 740i/iL & 540iA and are as follows: 740i/iL & 540iA = Charge pump - located next to the master cylinder. 750iL = Pre-boost pump and separate charge piston. These components are also mounted next to the brake fluid master cylinder and fluid reservoir. LOW BRAKE FLUID SIGNAL TO LCM DSC III HYDRAULIC UNIT PUMP MOTOR Introduction to DSC Hydraulic Charge Existing A5C+T and DSC II systems already perform hydraulic control regulation but do not require the additional charge pump systems. Why 7 The reason being those systems only actuate the rear axle circuits. Obviously the DSC III system has the capability to actuate front and rear axle circuits together which requires additional hydraulic fluid supply. For this reason, during an ASC or DSC regulation function requiring hydraulic interven¬ tion, the DSC III control module switches the electrical charge pump on to provide this addi¬ tional fluid. 740i/iL & 540iA Vehicles: When activated, the Charge Pump delivers a brake pressure of 10 -15 barto the front axle circuit of the hydraulic unit and into the front axle circuit pressure chamber of of the master cylinder. The master cylinder piston for the front axle circuit contains a notched restrictor forward of the central valve which allows excess fluid to return to the reservoir under a restriction. The pressurized fluid also acts on the rear axle circuit of the master cylinder. This provides the hydraulic charge to the rear axle circuit of the hydraulic unit as needed. LOW BRAKE FLUID SIGNAL RESERVOIR ta FLUID SUPPLY TO HYDRAULIC UNIT M \ i FOR ALL OPERATING CONDITIONS ,, CHARGE PRESSURE Y J Introduction to DSC 750iL Vehicles: The electric Pre-boost pump delivers a brake fluid pressure of 7-15 bar to the isolated chamber of the charge piston. The pre-boost pump incorporates an integral pressure relief valve which opens at 15 bar. From the isolated chamber the fluid returns to the reservoir through a restriction. The restriction causes pressure to build in the chamber which pushes the pistons outward. This immediately acts on two valves which block the normal braking circuits that flow through the charge piston ports. The pressure in the isolated chamber continues to push the pistons outward delivering the required charge pressure. LOW BRAKE FLUID SIGNAL TO LCM PRE-BOOST PUMP IVIMO I Ch CYLINDER RESERVOIR MASTER T 0 0 0 0 o o o o o d j*u/ ^ L fTO s (ioo TK ■ be-* - LJ - i 7 1 - r FLOW LIMITER CHARGE PRESSURE SIGNAL CHARGE PISTON t FLUID SUPPLY TO HYDRAULIC UNIT FOR ALL OPERATING CONDITIONS For ABS and CBC operation, the pump systems are not switched on, only during ASC/DSC regulation requiring hydraulic intervention are the pre-boost pump or the charge pump switched on. The balance of the hydraulic system functions operate in the same familiar manor of all previous systems. The individual brake circuits can be isolated as needed to restore lateral locating forces through pressure build, hold and release phases of operation. During an ASC hydraulic intervention requiring only rearwheel brake application, the inlet valves for the front wheels are closed preventing any pressure influence from the charge pump systems. 22 Introduction to DSC LOW BRAKE FLUID SIGNAL RESERVOIR DSC III HYDRAULIC UNIT J MASTER CYLINDER CHARGE PRESSURE SIGNAL CHARGE PUMP PUMP MOTOR PRELOAD VALVE CHANGEOVER VALVE PRELOAD VALVE 0 0 um nm v« •v v« •v LEFT , „ REAR [ tfr BRAKE LEFT FRONT BRAKE RIGHT FRONT BRAKE Introduction to DSC Principle of Operation Dynamic Stability Control Systems Introduction Dynamic Stability Control (DSC III version 5.3) was introduced on the 1998 M odel Year E38 and E39 - 540 vehicles. For M odel Year 1999, the system is enhanced with additional con¬ trol functions and a new combined rotational rate/lateral acceleration sensor as version 5.7. It continues to be offered as standard equipment in the E38 and E39 - 540 models. The new functions are titled as the Dynamic Braking System and include the: Dynamic Brake Control (DBC) Maximum Brake Control (MBC) DSC III adds a further dimension to the dynamic stability control system. DSC II has the ability to mildly correct for lateral instability and only at the rear brakes when braking con¬ trol is necessary. DSC III has the ability to brake any wheel during cornering maneuvers where the control module's programmed limits for vehicle oversteer and understeer are exceeded. New sensors are added to the DSC III system to monitor the rotational rate of the vehicle around its vertical axis and a lateral acceleration sensor to monitor the side to side forces on the vehicle. The hydraulic system of the DSC II has also been modified to allow brake regulation on the front wheels and to ensure that the supply of brake fluid for DSC II regulation is main¬ tained. Two different hydraulic systems are used on the Bosch 5.3 DSC system as follows: 740i/iL & 540iA use a charge pump for the front brake circuit. 750il_ uses a boost pump and separate charge piston for both the front and rear brake circuits. The hydraulic system used on the Bosch DSC III 5.7 has changed on the E38 and E39. The 750il_ now uses a similar hydraulic system tothe 740i/iL and 540i. The charge piston and pre-boost pump have been eleminated. The brake pressure sensor is now located in the hydraulic unit on all Bosch 5.7 systems. 24 Introduction to DSC Dynamic Stability Control (DSC III) All of the familiar braking and straight line traction control features and system communi¬ cation carry over from DSC II. Based on select high/select low logic, the DSC III control module selects a vehicle stabilizing strategy based on the specific input signal values it is monitoring at the moment. For all DSC strategies this begins with engine intervention to reduce torgue: Forthe 750iL this is handled via CAN communication, DSC III to EML to minimize the throttle angle of the DK motors (750il_). Forthe 740i/il_ and 540iA this is handled by direct DSC III activation of the ADS II throttle housing. If additional torque reduction is necessary, DSC III informs DM E over CAN to: a. Retard ignition timing b. Shut down the fuel injection to individual cylinders DSC III monitors under/oversteer conditions through the following components The driver’s desired steering angle - steering angle signal over CAN bus Vehicle speed and speed differential at front wheels - wheel speed sensors Dynamic forces of lateral acceleration and yaw placed on the vehicle. This is poss ble with these two new components. The results are as follows: £ VSTMICLC Of HwlFS CX-TT OF TURN -5JJQZ.es- FLLLY UNDERSTEER CORRECTION m DSC III 1, VEHICLE APPROACHES TURN - Di 'w& SL*£rS i-ftiQ lui'i'i - dm dppJcU 2. DSC III lhu&oIs a^ Undmwt Cnndlinn ^i/wirl on vntiidn npatHi, lrtiEpcri nillrii- ■ il ml luinnp angle, tafcerBiaD^tepratfcin lorces b-iu yaw angde. - Ergim- tcf-que induction duliue - i,-.'ii i".rl- j=iK rt nr.^kfl rM.ili¥lr< j WITHOUT DF.lT III - ragUbfed tyalz slow? Viihfie! aawn sa rod wen veihick! spaed;. lAlhixsl an spends, rmp !■". ItTin^lnr ttiry iThflreinhaL uehicip pivots- in isvoroi Oc^Titiri&d, ihi5 Pa into lum Introduction to DSC The expanded hydraulic control of individual wheel circuits is apparent when stabilizing a vehicle exhibiting an oversteer condition as follows: 3. VEHICLE COMES OUT OF TURN SUCCcSF LILLY WITH DSC 1. VEHICLE APPROaOES TURM AT HIGH RATE OF SPEED: - Dr her into turn arid applies drakes to slgwdpwn, ■70’j.Ur WITHOUT DSC 2A_ Late^. beaming faroei are diminisn^d dt iesi wheels high speed due z- esntmuga vehicle n: farce of lurn 2D. The torque reduction and rear nmhe regulFitnn should f.tah:il[?e ttie vehbfe fft this point, H noi me left front wtieel high degree gf lateral t>d&(;ng tgrge and & nK^entftniy legi/aled- This aetbn deibe r abey c-aasea Lhe wheel 1o stied a calculated cegree of it's boating fbroe. This counteracts mersteer yaw at Ihis wn=el ar-d also ads in 4lowrg tna vehicle dev.n lo corned ih 2'E. Driven ines lo compensate hy □uerstaering which dimnshes laleral bcatng force even lurlhef. EjmbltaneojsJy, rear of car starts to siice out. 2C, DSC H determines an OVERSTEER conddiDn. Er*iine torque i£ reduced via CAN Bus signalling. Outside “"ear wheel is mc^entarly nEgdialed to countered severe yaw angle 4a!sa helps to reduce drive torque lunherji Transmission system intervention also occurs during any A5C/DSC regulating phase. Through CAN bus communication the AGS control module is informed to delay any gear changes during regulation. This prevents any unwanted driveline dynamic changes during DSC regulation. Though DSC III provides state of the art, electronic correction of undesirable vehicle han¬ dling characteristics, it is important to remember vehicle stability is always subject to the physical laws of centrifugal force and extreme road conditions. Good judgement and common sense on the part of the driver are still required. Introduction to DSC DSC Features Corner Braking Control (CBC) CBC is a feature of dynamic stability control that is designed to improve the vehicle’s sta¬ bility if the driver brakes while driving through a curve. If the vehicle is braked while driving through a curve, an unequal braking force will be applied to the wheels due to the weight shift of the vehicle to the outside of the turn. Based on the vehicle speed and the speed differential of the two front wheel speed sensors, the control module can determine if CBC needs to be activated when the driver applies the brakes. If CBC is activated, the regula¬ tion will pulse the wheel brakes on the outside of the vehicle to provide an equal braking force on all four wheels. Dynamic Braking System (DBS) The dynamic braking system is designed to enhance the braking control of the DSC forthe driver of the vehicle. The dynamic braking control and maximum braking control are func¬ tions that are programmed into the control electronics of the DSC with no additional hard¬ ware changes. The Dynamic braing system features consist of DBC and M BC. Dynamic Braking Control (DBC) The DBC function is designed to provide the maximum braking force available during rapid (panic) braking situations. The DSC control module looks at the inputs from the brake pedal switch and the signal from the brake pressure sensor on the master cylinder. The criteria for activation of DBC is how rapidly is the brake pressure built up with the brake pedal depressed. The total criteria required for DBC activation includes: Brake switch ON Brake pressure build up >threshold value Vehicle road speed > 5M PH Vehicle not in reverse Not all wheels in ABS regulation If the threshold for DBC activation is achieved, the DSC control module will activate a pres¬ sure build up regulation phase through the hydraulic unit. The pressure at all wheels is increased up to the ABS regulation point. This occurs even if the driver does not achieve the ABS regulation point with the pedal. The rear axle brakes are controlled with select-low regulation and the front axle brakes are controlled individually. ABS regulation will continue until the driver releases the pedal and the pressure in the master cylinder drops below the threshold value stored in the DSC con¬ trol module. Introduction to DSC Maximum Brake Control The MBC function is also designed to enhance a driver initiated braking procedure. The M BC will build up the pressure in the rear brake circuit when the front brakes are already in an ABS regulation cycle. The additional braking pressure at the rear wheels will shorten the stopping distance. The following criteria must be met before the DSC control module will activate MBC: Both front wheel brakes in ABS regulation Vehicle speed > 5 MPH Vehicle not in reverse DBC and pressure sensor initialization test OK Rear wheels not in ABS regulation Introduction to DSC Diagnosis The following diagnostic functions are available using the DISplus or GT-1. Control Unit Functions: Expert mode diagnosis available at any time during troubleshoot¬ ing. To enter: press the Control Unit Functions button at the right lower corner of the screen. The contents are: • Identification • Delete Fault Memory • Read Fault Memory • Component Activation • Status queries (requests) Service Functions: Provides access to specialized test modules used as post repair procedures. To enter: Function Selection Service Functions Chassis Dynamic Stability Control The contents are: Connection Speed Sensor: A test to verify the proper wiring to the wheel speed sensors Connection Brake Lines: A test to verify the proper brake pipe connections to the hydraulic unit. Adjustment Functions: Test modules to initialize certain components after repair work is performed Steering Angle Sensor Fateral Acceleration Sensor Pressure Sensors Test Modules: Faults with the DSC III system can be diagnosed using fault or symptom driven test modules. To begin diagnosis: • Perform the Quick Test. • Select Vehicle Symptom from the Symptom Selection page. • Select Test Module from Test Plan page. • Press the Test Schedule Button. Introduction to DSC Coding Coding must be performed after replace¬ ment of the DSC III control module or the steering angle sensor. ZCS coding is found in the Coding and Programming selection from the start screen or when pressing the Change button. Follow on-screen instruc¬ tions for initialization of components after completing the coding process. Adjustment Functions Adjustment (initialization) is required when: Replacing the DSC III Control Unit. Replacing/Re-coding the Steering Angle Sensor. Replacing one or both Brake Pressure Sensors. Replacing Lateral Acceleration Sensor. Steering Angle Sensor The steering angle sensor requires an offset adjustment afterthe sensor has been replaced, coded or after repairs to the steering or suspension system. The offset adjustment informs the steering angle sensor processor of the straight ahead position of the front wheels. The adjustment is performed by completing the Test Module found in Service Functions. Once the adjustment is complete the sensor sends an identification number over the CAN bus to the DSC control unit. The ID provides confirmation that the steering angle sensor is coded and has successfully completed the adjustment procedure. Special Tools Special Tools available for the DSC III system consist of: Tool # Description Purpose 34 5 240 42 Pin V-Cable For B.O.B. 61 4 390 61 4 390 60 Pin B.O.B. For pin by pin diagnosis 34 5 160 Pressure Sensor Socket For installation and removal of hydraulic brake pressure sensor. 61 4 420 83 Pin B.O.B. For pin by pin diagnosis of Bosch DSC III 5.3 and ASC +T5 Introduction to DSC Review Questions 1. What are the primary differences between Bosch 5.3 and 5.7 ? 2. What is the nominal voltage output of the Rotation Rate sensor when the vehicle is at rest 7 3. What type of wheel speed sensors are used on the Bosch DSC III system on the E38 and E39 ? 4. List the required activation criteria for DBC activation: 5. List the required activation criteria for M BC activation: Introduction to DSC Review Questions 6. What hydraulic components are unique to the 750il with DSC 5.3 ? 7. What 2 DSC component are responsible for the increased dynamic control of DSC over DSC II? 8. List the locations of the hydraulic pressure sensor on the following DSC systems: DSC 5.3 (740i/iL and 540i) DSC 5.3 (750iL) _ DSC 5.7 (All) _ 9. Briefly explain Corner Braking Control (CBC): 10. What is the handbrake signal input used for on DSC III 7 Introduction to DSC