ABS issues

[JTodd]

I recently replaced a front hub - twice. Anyway, after putting the newest one one, I have noticed an intermittent problem with the ABS. Occasionally, the ABS will activate while rolling to a stop. Usually, the speed is less than 5 mph, dry pavement, gradual stop, low brake pedal pressure. I can feel the brake pedal vibrate and truck does not continue to slow at the same rate. I have tried to make it repeat, but cannot. This happens once every 3 or 4 days. The ABS indicator light does not stay on after startup.

Any ideas? I was under the impression that ABS 'turns off' at these low speeds. Is this more of a computer problem?

[chuckf]

JTodd,
When you installed the hub were you carefull not to pinch the ABS sensor wire between the hub and the back shield? If there is an intermittent problem it sounds like you may have pinched the sensor wire and it is grounding to the frame. Just a thought.

[JTodd]

It is worth a look. However, I was careful to route the wire through the cutout in the dust plate (is that what it is?) It will be easy enough to look for damaged wire sheath.

[Govt issue]

The last one that I had doing that was because the grease from the bad hub covered the sensor. The computer thinks there is a lockup condition, so it dosen't flag the light. Take it out and clean it. both of them. if that dosen't work have someone check it out.

[diesel65]

GM has a service bulletin about this problem, The ABS sensor is heaving due to rust buildup under the sensor.
Remove the hub you did not replace and clean the area where the sensor mounts, you might have to chip away any rust that the wire brush won't remove, then smear a coating of wheel bearing grease over the surface and reinstall sensor.

GM has a check procedure to see if that is the problem, you need to hook-up a AC scale millivolt meter at the connector in the wheel well and spin the tire by hand, not trying to spin it as fast as you can, just spin it and maintain rotation, you should see at least 350 millivolts.