Sysgen

I'm sharing my experience in fixing my ABS problem so as to help others that may have the same problem.

The ____!____ light was comming on after the car started moving. So right away that told me that the ABS control unit was ok and that the problem was with the speed sensors. But which one and why?

To easily find which one I did the following:

Disconnect the connector on the ABS control unit located on the passenger side, just to the right of the glove box by removing the two small screws circled in the first image.

Press the small ears circled on image2 to remove the connector. You end up with the connector on image 3.

Using an ohmmeter you should be mesuring ~1000ohm on each speed sensor.

Front Right, PIN 11 and 21
Front Left, PIN 4 and 6
Rear Right, PIN 24 and 26
Rear Left, PIN 8 and 9

In my case, the rear right, (which by the way is to your right sitting in the car), was mesuring 0 ohm, meaning that either the cable was cut somewhere or something was not connected correctly. it was the small connector below the rear brakes that connects the brake pads sensor and the ABS speed sensor, the cable was not pushed in correctly.

This procedure allowed me to find the problem in around 15 minutes, without having to remove every wheels

Stephane, '90 S2

951Boost

Great tip Sysgen, thanks for sharing.

Lanny Curlett

Thanks so much for that tip. The light doesn't come on until the car is moving so it must be a sensor and I will track it down using the described process. many thanks!!
Lanny

Rock

Hey hey! Same here! When that light is on, does it mean the ABS is disabled?

Sysgen

If the computer cannot detect all 4 wheel movement it disables the ABS. The ABS system relies on wheel speed to determine how much brake pressure to apply.

nickg

well if anyone needs abs parts, i have the complete setup and a few of the computers i'd sell cheap

rberry951

This thread sparked a question I've had for a long time, is there a safe way to disable the ABS and get real non-ABS behavior from the brakes? Just always been curious on this.

Sysgen

Disconnect one of the speed sensors

But you`ll always have the ! light on and the Antilock also.

Rock

Simpler, pull the fuse!

928NZ

If the ABS fails after you start moving it has failed it's self test. In my case it is probably the hydraulic ABS pump which attempted to cycle through a self test. It is not necessarily a speed sensor.

liveinadive1

Hi

This is my first post so apologies for it being asking questions.

I have classic ABS light on after moving fault.

I used Sysgen's method using a multimeter to check the four sensors.

3 are reading the same (0984) the last one reads slightly less (0956).
Would this be where my problem is coming from or would there have to be more of a difference in resistance for it to be an issue?

Sysgen

Welcome aboard, please specify where you are from in your profile, it's always nice to see.

I don't personalty think this small difference would make any difference. It's too small. Maybe if it was half.

Next step is to swap the ABS unit. I think I have one, would let it go for $50+shipping if you want it.

Let me know.

liveinadive1

Cheers for the quick reply Sysgen.
Have updated my details as you suggested.

OK cool, next step control unit.
Thanks for the offer but being in the UK after shipping it might work out quite espensive.

Sysgen

Indeed, shipping would be a killer

Good luck.

gregeast

I had similar issues: '!' on after driving and all the sensors had similar ohm readings. In my case the car had been in an accident and so I knew which corner to start at so I bought a used sensor fairly cheaply and it fixed the problem.

I do vaguely recall that the failed sensor looked different than the new (used) replacement, the magnet (or whatever that is) that protrudes appeared to be shorter on the bad sensor but it still had the same ohm reading as the others.