lloyd21

How do I diagnose a bad ABS pump module? At start-up I get a weird ticking sound, then an electric guitar string/or bell sound coming from the left side of the engine at start up when I apply the brakes.

Also I get a weird brake pedal vibration when coming to to a stop at start-up, like the car does not want to stop then at the last inch or so the brake pedal goes all the way down. This goes on to for a minute or so then my ABS-OFF light comes on and the problem goes away....VAG-COM cant communicate with the ABS system.

Would this be the ABS Pump Module, MC, brake bomb, or...? I pulled the ABS fuse then it works fine (with ABS-OFF light on). I also checked the ABS wheel sensors and they seemed fine.

Any ideas? TIA

closed loop

When you say start-up, do you mean the car starting up (ignition turning engine on), or drive-off? It sounds like you are getting ABS activations at low speed, end of stop events. This could be caused by the wheel speed sensor being too far away from the tone ring. As the vehicle slows down it gets harder for the sensor to pick up the tone ring edges if it is far way, and will then read zero. This makes the ABS module think that a wheel is locking up and it will dump the pressure out of that wheel. This will cause noise and pedal feedback.
This same issue will also effect the EDL function, i.e. brake based tration control.

lloyd21

I mean actual drive off. Do you know the part number of the wheel speed sensor? Thanks