Hi. 1995 audi 90 quattro has abs off light on. it comes on when you start the car and it stays on while driving. any way to diagnose? also, does it effect the all wheel drive from working properly? dont think it should but you never know.

 

the ABS sensors at the wheels get dirty and I have heard that there is a method to clean them and reseat them, that's assuming that the sensors themselves and the wiring for them is intact at each wheel back to the ABS itself!

 

You are correct, the sensors may just need a good cleaning. You can buy a can of carb cleaner from any auto parts store. However, to reach the sensors, you will need to remove the axles from the wheel hubs. The sensors are inside the hubs and are little silver dots that probably have some build up on them.

If the car is a Quattro, it may also be an issue with your differential. Although this is unlikely, the ABS is automatically turned off when the "DIFF" switch is depressed, if your vehicle is so equipped. If you feel the front steering of the car is no longer "sticking" to the road (as Quattros do) then your electrical system is having issues. I believe your car is an OBD I vehicle, so if you have an adapter you can get a scanner and it may tell you what the issue is.

Hope this helps!
Hope