# Is airgap important for front abs sensor?



## death 4kqt (Nov 24, 2007)

I have a 99.5 a4 1.8tq
I just did a front wheel bearing on my a4 and I pulled my abs sensor out because I was doing a bit of welding on the old bearing outer race to shrink it and slide it out and I didnt want to get the sensor hot. The sensor came out pretty easy and I pushed it back in until it bottomed out. Also, I started the car once with the axle out of the knuckle to make sure the welding didnt fry anything. After I drove the car for a couple miles the abs light came on and is now on all the time. The red brake light is not lit. It doesnt seem like I physically messed up the sensor, but I am wondering if you need to set an airgap on them, I tried pulling it out about 3 or 4 mm and drove around but the abs light remained lit. Ever hear or airgaps being important for these? Do I need to clear the code or will it go away when I fix the problem. I am going to borrow a cheap ebay VAG scanner tomorrow and see what code it gives me. Should I just order a new wheel sensor now, or is there hope and I just need to get the air gap set perfectly. Never had and issue like this with my older audis, but I havent dealt with a b5 abs sensor before.


_Modified by death 4kqt at 4:50 AM 12-11-2009_


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## GTijoejoe (Oct 6, 2001)

*Re: Is airgap important for front abs sensor? (death 4kqt)*

If it was rubbing is possible that the sensor heated up and destroyed the IC in the sensor head.
Yes airgap is important, normally they are within 2mm's (being larger is rare, but possible with specific sensors most likely NOT yours). Being too close can also cause a doubling effect which gives faulty signals.... normally the doubling effect will not cause it to flip a fault code, but rather give faulty signal and faulty ABS/VSA actuation.
Being too far away makes the signal weak, and flips a code.
I'd put my money on
A) the sensor being busted
B) the pulsar ring being busted (if the sensor was rubbing on it)
Take it from there and see what you got http://****************.com/smile/emthup.gif 


_Modified by GTijoejoe at 7:40 PM 12-11-2009_


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## death 4kqt (Nov 24, 2007)

*Re: Is airgap important for front abs sensor? (GTijoejoe)*

I scanned the abs codes today with a vag com knockoff scanner and it said "driver side sensor: open circuit"

sounds like I busted a wire in the sensor's coil when I wrenched it out. I ordered a new one today. Will update when I throw that in.


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