ABS operation
I'm having trouble with the ABS on my Rover 75 diesel estate auto. When I brake at slow speeds, the ABS goes off and on. This does not happen at high speed, so I fitted new brake discs all-round and checked for run-out with a DTI gauge. Everything came up fine, so I replaced the ABS sensors. No faults appear on the dashboard. I also checked with a PCAM tester and everything is clear. Do you have any idea of how I can fix this issue?
Michael Odare
As you say you have replaced the discs in an effort to resolve the problem, I am taking it that you are experiencing a judder on the pedal as opposed to the ABS light going on and off.
If the problem is due to the ABS system, this will not be affected by the runout of the brake discs, so investigation into the system will be needed, as opposed to checking the mechanical condition of the brakes. You do not mention the year of your Rover, but one of the most likely reasons for the ABS problem is that the magnetic pickup ring on one of the bearings is failing. Discovering which one may be difficult as the problem is intermittent, but you can check with a scanner that can display the live data or by using an oscilloscope.
If the problem is not sensor- or pickup-related, it may be due to a wiring or ECU issue. There is a known flaw with the wiring loom on the Rover 75 filling with water, which can then rot the loom and ECU connections. Check the loom as it runs along the nearside chassis and the area under the battery. Be cautious if the wiring has corroded as disturbing it may break any connections.
Last, the problem may be with the ABS unit itself. The pump and control unit are combined in one unit on your Rover and this may need repairing.