A couple weeks ago the ABS and ETS OFF (Enhanced Traction System) lights came on in my cavalier. They sometimes come on when the car is first started and stay on, sometimes they'll come on randomly while driving and stay on for the rest of the time the car is running, and sometimes they won't come on for an entire day of driving even under near-identical conditions. The brakes themselves are still good and everything else runs fine. The lights are always either both on or both off, never one or the other. The shop near me quoted $50 just to hook up a machine to diagnose it plus whatever it costs to fix it assuming they could find a problem. I've tried leaving the battery disconnected for 30 minutes hopeing it would reset the computer but it didn't help. Any ideas?

 

autozone might be able to scan it for free

 

most likely wheel speed sensor, or wiring going to it. just as a free, easy check, start car and wiggle wiring going to each wheel speed sensor (one at a time) it the light comes on as you are moving these wires, then you are getting close to the problem, wheel speed sensor themselves can be checked, but you need to be able to use a multi-meter. and gm has a spec for the resistance of the sensor from one revolution of the wheel in 1 second, but i can't remember it. hope this helps