ABS Brake Indicator - How to test for failing sensor?

[Spinman]

My ABS waring light illuminated way back when the car was new - resulting in a new front wheel sensor with only 2,000 miles. Now with 85,000 its starting to happen again. 35% of the time, when I start the car - the warning light is on and the traction control is off. The following vehicle restart, the lights are off - and everything seems normal.

Found this info a few post back...

>>also now the "abs" brakes indicator light has been popping up freqently

"Common GM problem related to Wheel Speed Sensors in ALL GM cars. These sensors break easily causing traction control and ABS problems. The front ones are prone to most damage, typical replacement cost is about $20 on normal cars, unfortunately on Aurora's you cannot change the speed sensor without changing the entire Wheel Bearing, this is about a $110 fix per bearing (you'll need to do atleast the fronts). Labor shouldnt be anymore then $50/ per bearing. They probably need repaired anyways on a 116km car, this will also fix any buzzing sound you hear coming frm the front on the highway. If your hard up for cash you get along for awhile with this problem. Your bearings really probably do need replaced. I've heard of people running cars for 2 or more years with the problem apparent. You might make it happen less frequently by turning off the traction control for now on. "

Already had new front wheel bearings installed at 65,000 - constant wineing sound.

Was wondering how I might be able to test the sensors to determine which one is going bad (Is this a home mechanic test - or would I be better off going to the dealership once the sensor is constantly on and unable to be reset)....

Thanks -

Appreciate any thoughts or suggestions...

[bustedratchet]

You can test it with an ohmmeter to check resistance and if you get lucky you might find a bad one. Or with a labscope to watch the electrical wave form.You could check the wheel connections and wiring maybe something clipped a wire. You might have to get it checked out other parts in the ABS system could throw the light on.

[Spinman]

Thanks for the thoughts -

I just ordered the shop manual from the library - I'll read up on the issue and see what the diagnostic test flow looks like. Anything beyond a resistance check probably means that it is a garage repair item..