Faulty Signal

Faulty signal

Checking the wheel sensor and pulse wheel




- Ignition off
- Remove the wheel for better access.
Check that the relevant wheel sensor is mounted tightly against the shaft or hub. Check that there is no dirt between the sensor and mating surface.
Check that the magnetic pulse wheel is correctly secured and free of damage, scratches (for example scratches, deformation).
Remedy as necessary.

Other information
- Transmission input speed sensor rear wheels Transmission Input Speed Sensor Rear Wheels
- Transmission input speed sensor, front wheels Transmission Input Speed Sensor, Front Wheels





Was a fault detected?

Yes - Verification

No - Checking the brakes and wheel bearings

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Checking the brakes and wheel bearings

Hint: A sticking brake can block one or both wheels when the car is being driven. This will mean that the wheel sensor signal is not transmitted.

Check that the brake calipers are not sticking and locking the wheels.
Check the wheel bearing on the relevant wheel for play. Check that the wheel rotates freely and is not sticking. If the wheel has too much play, especially check the mounting of the hub on the spindle.
Remedy as necessary.

Other information
- Brake pads, front, B5254T7, AW55-50/51SN, B5254T7, M66 Brake Pads Front, Replacing
- Rear brake caliper, B5254T7, AW55-50/51SN, B5254T7, M66 Service and Repair
- Rear wheel hub, M66, AW55-50/51SN Rear Wheel Hub, Replacing





Continue - Verification

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Verification




Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the components, connectors, etc.
- Ignition on
- Test drive the car according to: Test Drive Form (DSTC (dynamic stability and traction control) /brake control module), description Test Drive Form (DSTC (Dynamic Stability and Traction Control) /Brake Control Module), Description
Check the ABS warning lamp during the test drive.
If the fault has been remedied the lamp will go out when the speed exceeds 20 km/h.
If the warning lamp does not go out, return to the workshop and read off the diagnostic trouble codes (DTCs).

Does the ABS warning lamp go out and remain unlit?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information

Attempt New Test - Checking the wheel sensor and pulse wheel

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