Specifications

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Testing Testing ABS and Traction Control Systems
• On most systems, the ASC or DSC dash lamp will be ON with the system disabled and the
control switch in the OFF position.
• The ASC/DSC dash lamp flashes when the system is active. The lamp stays on solid if a fault
is stored.
• Low Brake Fluid may turn the ASC/DSC lamp ON along with a red brake lamp
• With the ASC/DSC system OFF, the ABS system is still ON or activated
• Fault codes for both ASC/DSC and ABS faults are stored in the integrated ASC/DSC/ABS
controller. Use the ABS menu selection on the scan tool to access all fault codes.
• For Bosch 5.7 DSC III (E46 all-wheel drive), turning the DSC button “OFF” only deactivates
ASC engine and DSC yaw intervention. Brake intervention remains active for anti-spin control
in slippery conditions.
• For Bosch 5.7 DSC III (X5), turning the DSC button OFF deactivates the DSC yaw
intervention only, not the ASC engine intervention. Engine traction control intervention
remains active as well as brake intervention for off-road operation.
Important Tips for Testing ABS and Traction Control
• When the scan tool is accessing the ABS system, the ABS warning lamp may illuminate. The
lamp may stay on until the scan tool is disconnected and the ignition key is cycled.
• In most cases, the BMW ABS systems will not communicate with the scan tool if the vehicle
is driven.
• If the battery voltage drops below about 11.8V, the ABS/DSC system may have problems
communicating with the scan tool.
• For 1992–95 systems with ASC, a malfunction in one system may turn on the warning lamp
for both ABS and ASC.
• ABS or traction control codes may sometimes also turn on the engine MIL.
• ASC/DSC codes may also turn on the brake lamp (hydraulic problem) which should go out
when codes are cleared.
• On systems with integrated ABS and traction control, clearing ABS codes with the scan tool
also turns off the ASC/DCS fault lamps.
• Late models equipped with DSC may have a special warning lamp usually located between
the speedometer and the tachometer.
• For vehicles equipped with ASC, always turn the ASC switch off during dynamometer testing
or a fault code will set and the warning lamp will stay on, though it should go out with next drive
cycle. Vehicles with DSC-III can be safely tested on a dynamometer without any problems.
IMPORTANT:
Antilock brake diagnosis with the scan tool does not require opening the hydraulic system or
disassembling mechanical parts. Complete antilock brake service, however, may require opening
the hydraulic system. Antilock brake hydraulic systems operate with pressures of approximately
2000 psi or higher. Some systems may need to be completely depressurized before opening any
hydraulic connection. In most cases, you can depressurize the system by applying and releasing
the brake pedal at least 40 times. Follow BMW service manuals for specific ABS type hydraulic
system service and safety instructions.