Antilock brake system (ABS) diagnosis, function check

AD42.30-L-3003A

Antilock brake system (ABS) diagnosis, function check

22.9.97

Antilock brake system (ABS) diagnosis, previous knowledge

AD42.30-L-2001A



Carry out tests below using STAR DIAGNOSIS on the roller dynamometer or with wheels raised.

After switching on the ignition, the ABS MIL must go out after approx. 2 s.



If for the last journey there was a dynamic rpm sensor fault ( - ), which has since been corrected or the control module has been replaced, the ABS MIL will only go out above a vehicle speed of 5 km/h, because only then is the internal rpm sensor check completed.

Function check

Test step

Inspecting

Note

1

Assignment of the rpm sensor

Drive all wheels individually one after the other. The wheel speed for the instantaneously driven wheel must be calculated.

AD42.30-L-3004A

2

Airgap

Slowly accelerate all wheels individually, by axle or together. Above a certain wheel speed, a speed value must be calculated for each driven wheel.

AD42.30-L-3004A

3

Assignment of wheel brakes

Press brake pedal until the wheel is only able to turn with difficulty (roller dynamometer brake power 1 kN). Switch on inlet valve of wheel concerned and increase brake power. The wheel must continue to be able to turn with difficulty (constant roller dynamometer brake power). Switch on outlet valve. The wheel should turn freely. Switch off inlet valve again and check the next wheel in the same way.

AD42.30-L-3011-02A

4

Test drive

If the tests above revealed no faults, exit diagnostic mode and accelerate the vehicle to above 5 km/h. At the latest at this speed the ABS MIL must go out and remain switched off.

Then drive the vehicle faster than 50 km/h for at least 80 s. Only then are the internal system monitoring procedures completed.