Dark Blue

Hi, I have an '89 S4 Auto. After some brake work performed by an independent shop and several mos sitting around, my antilock warning light is coming on. I want to check the relay first. Can someone remind me which relay it is. Also, before I buy a new one from Roger, is there anything simple I can do to test or unstick the one I have. I replaced it around 15 years ago when the antilock warning was coming on and it fixed the problem that time. Thanks for any help diagnosing this problem.

Steve
'89 S4 Auto

GregBBRD

The most important detail to know, when diagnosing the ABS system without an ABS system tester:

Does the failure warning come on with the key, or does it only occur once the vehicle is moving?

jstadter

Greg - would you explain the implications of one failure warning vs the other? I have to deal with an ABS warning on my '88.

Mrmerlin

Jim, please tell us,
when does the light come on ?
After the car has started rolling over 4 mph?

or once the key is turned to crank then run.

with this information it will be easy to point you in the right direction.

NOTE trying to advise you without this information means it can be different things to look for.

jstadter

My light comes on once the key is turned to crank then run. I replaced the relay a while back and that solved the issue, but the car has been sitting for a while since then, so maybe I need to Deoxit the relay terminals. I am curious though about the different implications between the two failure modes.

SeanR

Stan means to say, does the light come on and stay on after the car has started, or does it come on only after you start rolling down the road. With the key turned on and car not started, it's going to be lit all day everyday.

Mrmerlin

Thanks Sean, your correct.
its funny you have to beg for information from people that want to find out how to fix something.
Anyway based on the post 5 info the relay in the CE panel has failed.

I would suggest to replace the ABS fuse first, then test it.
Then disconnect the battery then tighten the ABS phillips screw at the left front fender anchor.
then test ,
if no joy take the ABS relay apart and look for a small wire that has been melted or a bad solder joint

Wisconsin Joe

If it comes on immediately after starting the motor (disregarding the bulb check), it's most likely 'systemic'. Relay or module.

If it doesn't come on until the car starts to move, then it's most likely a wheel sensor issue. The control module 'sees' the wheels turning. If it senses one turning well out of tolerance (doesn't sense one turning at all), then it signals a fault.

polecat702

When my 89 is on the lift, I can put it in drive and the ABS light stays off. Does that narrow it down to just the front wheels? Before the car sat for a year, the ABS light was never on after the bulb ck.

ALKada