ABS over-reacts, then ABS inop (not a false alarm)
 

When I'll start to go somewhere, my ABS usually acts up while going down my driveway. My driveway is actually about 1,000 feet, all gravel, going downhill. I usually ride the brakes a lot, which gives it a good chance to mess up, especially on the gravel. Some days, my ABS will start to kick in and let the tires slip while going down my driveway. It has also happened while driving on the road, usually not to long after I've just left my house. The "low trac" light comes on when ABS is letting the tires slip, specifically in situations where it shouldn't.

Then after this, one of two things happens:

1. The ABS INOP light comes on and the ABS system does not operate, but normal braking is fine.

2. The ABS INOP light does not come on and ABS works.

Where do I start to fix this problem?

If the ABS inop light came on there is code stored in the PCM. You have to retrieve it. Unless it's a soft code.

2nd, a soft code that resets itself is usually a wheel sensor. If the wheel sensor is going bad, this would also account for the system applying the ABS when it was not supposed to. You should pull the code and while your there, monitor in real time, the wheel sensor signals. This will tell you exactly what is going on.

One sensor that goes bad quite frequently is the rear one in the differential. A lot of times it gets metal particles stuck to it from wearing gears. Cleaning it can help.

BTW, you didn't do any wheel or brake work lately did you? Maybe if so, someone bumped something while they were there.

Dave

Also check the ground terminal on the passenger side just behind the battery. It's the wire lug next to the red plastic "positive" box on the passenger fender. That being loose can cause ABS/Airbag problems as well.

It is a soft code because the light doesn't always stay on. Sometimes ABS doesn't over-react and it works fine. Others, it messes up and then ABS INOP happens. I had already suspected it was a sensor somewhere, I just didn't know where to check. I'll look at the rear differential sensor. And I haven't done anything to the brakes.

If you do not have traction control, then there are only 3 sensors. One in the Diff and one at each front wheel. There is no way to test them other than with a data scanner. Check them visually for damage or bad connectors. Be sure to unplug and inspect the pins and the entire length of wire from connector to sensor.