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View Full Version : 1988 Audi 100 C3 ABS Sensor Problem, Help Needed!



deko
25-02-2010, 02:04 PM
Hi folks,can anybody help me here,i have audi 100 avant 1988,c3 on the log book with a near/side/ rear abs sensor fault,when i start it up the light goes out but when i drive it the abs light comes on and failed the mot!Ihave tried to get a replacement (p/n 0265001060)but they say they dont make them any more,what to do next i dont know regards deko.

:beerchug:

zollaf
25-02-2010, 02:08 PM
if the light goes out, then the sensor should be working. try giving the end a good clean.

deko
25-02-2010, 02:13 PM
Yes the light goes out, i cleaned it up with some wd40 and a rag, but still comes on after about 40 yards of driving and stays on.

zollaf
25-02-2010, 02:17 PM
ok. the abs ecu runs a test on its systems, and if ok then the light goes off. for some reason its then picking up a fault. i would now check the abs ring for any damage/ rust. also check the air gap.

deko
25-02-2010, 02:30 PM
When you say rusty do you mean corroded badly or surface rust?

I tried to clean it up with a wire brush as best poss.....cleaned off loose stuff.....

The problem could be the car has been sitting for 2+ years as it was fine before this, and now this is the only problem i have

zollaf
25-02-2010, 02:40 PM
when you drive, the abs ring running close to the sensor causes a voltage to be induced in the sensor. the ecu then knows how fast that wheel is turning. if it locks up, the voltage drops to 0v and the abs kicks in. if the ring is damaged then the ecu checks all sensors when you start the car. the light goes off because everything is working. but when you start travelling, if there is too much of a discrepency between all wheels, the ecu doesnt know whats going on. the ring could have a crack in it, or a tooth missing. this is where an oscilloscope comes in handy because you can take reading from all 4 sensors and get an idea of whats going on. i would suggest though that the ring will be corroded too much to work, especially if shes been stood for two years.

deko
25-02-2010, 03:26 PM
When measured with a multimeter there is a resistance on all 3 sensor plugs leading to the sensor apart from this one.....this one seems very odd in relation to the other 3.....

Thanks for all your help so far mate :beerchug:

zollaf
25-02-2010, 05:16 PM
thats very strange, indicating a problem with the sensor itself. are you measuring from the sensor plug or from the ecu connector ?..