ignition BMW X5 2002 E53 DSC System Workshop Manual

7
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 torque:
•For the 750iL this is handled via CAN communication, DSC III to EML to minimize the
throttle angle of the DK motors (750iL). For the 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 DME over CAN to:
• Retard ignition timing
• 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 possible
with two new components which are discussed further on. The results are as follows:

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DSC III COMPONENTS
HDC SWITCH
The hill decent control function is activated by
pressing the HDC switch located in the center con-
sole. The LED will come on steady when the func-
tion is in standby and flash when HDC is regulating
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 III control
module to switch the system off (DSC indicator in
cluster illuminated.) When pressed again, the sys-
tem switches back on (DSC Indicator in cluster
goes off.)
WHEEL SPEED SENSORS
• 2 wire Hall Effect Sensor - “Square wave generator”.
• 48 pulse incremental wheel incorporated in wheel bear-
ing cover for contaminant protection. 48 pulses = one
complete wheel revolution.
• Stabilized 8 volt power supply to hall element on one
wire, ground path for sensor through second wire back
to control module. Signal is generated by the pulse
wheel affecting voltage flow through hall element creat-
ing a low of .75 and a high of 2.5 volts.
• Sensors identical to DSC II and ASC V systems.
• Sensors provide immediate vehicle speed recognition.

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DIAGNOSIS
Diagnosis and troubleshooting of the DSC III system is carried out using the DIS Tester or
MoDiC. The DSC control module performs a self check every time the ignition is switched
on. The warning lamps for DSC and ABS will remain on during the self check.
Any faults with the system will cause the lamps to remain on when the engine is started.
Faults that only effect the DSC operation will cause the DSC warning lamp to remain on,
however ABS can still function.
If the battery has been disconnected, the DSC warning lamp will remain on until the vehi-
cle receives road speed signals front the front wheel speed sensors and the steering angle
sensor can calculate the direction of travel.