Audi Repair: ABS light on - Audi A4 1.8 1998, rubber grommet, drive shaft

Question
Hi Naushad,

I just had my control arm and rod changed for both front wheels. Since then, the ABS light has come on and stays on. Doesn't blink though. Could it be a sensor that has come loose? If yes where is this sensor....can it be checked without having the car on the ramp? Got this done by a local garage - was cheap and they don't have any diagnostics!

Cheers in advance.

Answer
Hi Ranja,

Yes i think that there is a sensor loose, or if not then the fault was picked up when the work was carried out, somebody must have switched the ignition on when a sensor or 2 was disconnected.

there are normally 3-4 sensors attached near the arms, there is one speed sensor for each wheel that is attached to the hub and can be seen behind the brake disc. these sensors are normally attached by blots fixed onto the hub BUT some times some are a push fit without any bolts holding them in place. these types normally come loose when work is being carried out on them and they move away from the pulse ring attached to the drive shaft hence not working correctly.

then there is normally an angle sensor attached on one end to the chassis and the other end is attached to the lower front arm. check that the socket for this sensor is attached and also the arm that links the sensor to the arm is made of plastic(usually blue) so check  that it is not broken,

And again check that all the sensors are not damaged, as can happen when an over enthusiastic mechanic uses force!!!!

as for the speed sensor check that it is sitting all the way in the hub, give it a slight tap with a plastic hammer or a piece of wood (not too hard) to make sure they are all the way in,(the rubber grommet should touch the hub,

All this work can be carried out by removing the wheel, just make sure  the vehicle is stable before sticking your head under it!! use vehicle stands if possible.

As for the light you will need access to diagnostic software as the faults will need to be erased to make the light go off. the ABS system is a safety issue and the light remains on even if the fault is no longer present so the workshop can check for any faults when the vehicle is brought into the workshop. try locating a VAG-COM owner in your area, some charge a small fee or even do it for free to carry out a diagnostic. check VAGCOM forums.

hope this helps