Actions Before Replacing ECU

When all the checks have been carried out according to the action sequence under the relevant trouble code without any faults being discovered, it is logical to assume that the Electronic Control Unit (ECU) is defective.

As the ECU is a very high-quality and expensive component, it is important to be as sure as possible of the diagnosis.

The following steps must therefore be carried out carefully before the Antilock Brake System (ABS) ECU is identified as the cause of the fault.

1. Check the following:
- Correct wheel size
- All wheels are of the same height/width
- Correct air pressure in all wheels
- No play in wheel bearings.
Check once again that all the steps in the fault diagnosis routine concerned have been carried out.
2. Study the wiring diagram of the circuit concerned and familiarize yourself with how it works.
- If necessary, consult the relevant parts of the technical description and the electrical description of operation.
3. Check all the grounding points.
- If you have done this previously, do so once again.
- Check that power ground and signal ground are electrically separated.
4. Check the power supply to the ECU.
5. Clear the trouble code. Test-drive the car again.
- If the original fault persists, the ABS ECU must be replaced.