I have a 1996 GMC Yukon with 243,000 miles on it. It has had the following issue for some time: Start the vehicle, all is well. Put it in gear, begin to roll about 3-5 MPH, can hear the ABS system pulse once, then the ABS light remains on until the vehicle is shut off. This happens 95% of the time. Trying to figure out if this is an issue with a wheel speed sensor, or the ABS unit itself. Any Ideas?
Thanks
Your vintage of GMC truck has a history where rust can form under the wheel speed sensor mounting surfaces. This rust causes the plastic wheel speed sensors to become misaligned with the tone rings.
The fix is to remove the wheel speed sensors and inspect the plastic mounting flanges for the sensors to if they’re deformed from the rust. If they are then sensors need to be replaced. If the sensors aren’t damaged, then clean the mounting surfaces of rust, apply an anti-seize compound to the mounting surfaces and reinstall the sensors.
Tester
The ABS system can be scanned for codes, but a shop will have to be the one’s to retrieve them. An auto parts store code reader most likely will not read ABS codes. Anything else is simply a guess.
However, a common source of ABS errors are gummed up sensors and encoder rings. Cleaning these may correct your problem. Otherwise, I’d get the codes read before spending any money on parts.
I actually found an article on the problem. http://forums.trailvoy.com/showthread.php?p=1179929
Tester
Today I took my '96 Yukon to Midas to have them run the ABS code for free- It seems that their diagnostic equipment would not link to the truck. They said maybe the GMC dealer would have different equipment that would. My thought: Does this mean that something in the ABS control is fried? Any thoughts?
Thanks
@ffej take your truck to the GMC dealer.
They have the equipment and information to diagnose and repair your vehicle properly.
As said above, testing the GM ABS probably requires more than just the generic OBDII code reading equipment. The dealership would have the correct equipment to do the diagnosis, but a good inde shop might have it too. I’d be inclined to prefer a well equipped inde shop for this problem, as they’d be more likely to have ABS diagnostic and repair experience on older vehicles. The dealership shops – though it is probably the case they could easily figure out what is wrong on this vehicle – they tend to focus their att’n and training on warranty repair on newer models. As mentioned already, the problem is likely that one or more of the sensors is failing to produce the required reading for the ABS computer to work correctly. It may be a sensor failing, or it may be an electrical connection is corroded, or just a wire has broken. There’s a chance it is an actual hydraulic problem which could affect even non-ABS braking performance, so it needs to be diagnosed and repaired in short order.
But there’ll always be veteran mechanics at the dealer who are comfortable and competent working on these older vehicles.