I had this problem ever since I bought my car 7-8 years ago. The ABS light turns on rather randomly. Sometimes it stays off for months. Sometimes it turns on and of multiple times per day. It's a Ford Focus 1.8 tdci from 2004, 100 HP.
I did check the following:
- brake fluid level and cap checked (replaced with one from another car to see if the problem disappears, it didn't)
- DTC error codes read with Forscan: no error codes in general, no error codes from the ABS module. The only place in the OBD scanner tool where I could find something remotely related to this problem was the "ABS warning indicator" which was consistent (on/off) with the warning light on the dashboard
- reading ABS data while the vehicle is moving: all wheel sensors give the same speed reading in a straight line (with the ABS warning light on or off)
- performed the Forscan OBD ABS troubleshoot test: the test performs ok and no errors are found
- sometimes, after washing the car, the ABS light stays off for some time
- I tested the car during winter: the ABS works even if the ABS warning light is on
I'm not sure what to do next in order to solve this problem. I have a few questions
- Is it possible that I have a faulty sensor even if the speed read for each wheel is consistent with the speed of the vehicle? Can sensors be bad without giving error codes?
- What are your suggestions regarding what I can try in order to isolate the problem?
- Is it possible that this is a dashboard problem? I took it off and saw some bits of corrosion on some of the nodes on the electronic board.
- If the ABS module is available in Forscan for the live-sensor data, that means that DTCs should also be available, if present? Update: I took one of the sensors off and managed to get an error code. Therefore, indeed, the ABS light stays on without any error code.
Thank you in advance.