The common suspect is a front wheel bearing. GM has been using this design since the mid 1990's and owners have had a real lot of problems. The anti-lock brake wheel speed sensors develop real wimpy signals to start with. When a little normal play develops in the wheel bearing, it lets the sensor move away from the tone ring. That makes the signal become even weaker, to the point the computer cannot read it. The signal also becomes weaker as wheel speed slows down. Once the signal drops out, the computer thinks that wheel has locked up, so it tries to modulate braking power to it. The computer also knows that wheel cannot be locking up when you are not applying the brakes, so the signal dropout is detected as a problem. In response, it sets a diagnostic fault code, turns itself off, then turns the warning light on to tell you.
The dealer's scrap metal bin is full of these wheel bearings. New ones commonly develop the same problem in as little as 15,000 miles. The good news is the old bearings will work fine on a different car that does not have anti-lock brakes.
Saturday, January 27th, 2018 AT 4:32 PM