Without provocation, the ABS fault indicator light came on in my 2003 S-10 after it spent an hour sitting in the sun. The truck is a 2WD V6 extended cab model with disc brakes in front and drums in the rear. The ABS system presently can't decide if it's broken for sure or not. When the light's off, it will demonstrably work. When it's on, it doesn't.
I have started to investigate the problem and obtained some wiring diagrams from the factory service manual. While doing that, I've noticed something extremely interesting. The window sticker for the truck *claims* that it has four wheel ABS. However, the only obvious sensors and related wiring are on the *front* wheels. There is no immediately obvious way for the ABS system to sense a loss of traction for the rear wheels during braking!
This seems odd, and it would also seem to nullify the claim that the ABS system is "four wheel ABS". So...how does that work?
03 uses either the vehicle speed sensor OR a sensor on the rear axle for the ABS.
It will have a stored code to tell you why the light is on.
The common problem is the backing plate rusts and moves the sensor away from the tone ring. Next most common is the connector gets corroded and the next is broken wires in the sensor cables.
(yep, here I am over a month later...the group sure is quiet any more!)
I took it to the dealership branch here in town and immediately got the feeling they just didn't want to deal with it. Even when I said I'd pay for the diagnosis, they couldn't be bothered. "Oh, take it to Autozone...they can read the code."
As I found out, that's not true. Or at least the two guys at Autozone didn't think their code reader would do it, and they seemed to know.
So I bothered my brother and let him take the truck to his automotive class one day. It's the left front wheel sensor or its wiring. I paid him $20 for his trouble (pay attention, dealership guys!).
The light's on practically all of the time now. Only rarely does it go off. I guess that one of these days I'll pop the wheel off and see what I can find.
Few of the cheaper Home Tree Mechanic OBDII scanners will do ABS. It is starting to become more of a option these days on cheaper scanners, but they are still pretty limited. If it's just a ABS sensor on one of the wheels, that's a easy enough fix. Most of the time in these cases it's just a bad Sensor. Usually the cable gets Damaged. The backing plate rusting and moving the sensor out of the way to not pick anything up would be pretty rare. It would have to be pretty BAD, almost hanging off. You also would normally get a different code for a Damaged ABS sensor and one that's not picking up the Tone Ring.
For example, if your ABS sensor is Damaged, your ABS Self check will fail without the Car even moving which will turn the light on and stay on without the Car even moving. On the other hand when you start the car, the ABS light goes on and self tests and then goes off while your just sitting there, but then turns on after driving down the street just a bit, then it could be a Damaged Sensor or a Tone ring Issue. In my experience, 90%+ of the time, it's a BAD SENSOR someplace on the car. One time I had a Hummer H2 with bad front bearings. Well the ABS sensor and Tone Ring are in the Bearing. After Replacing the Bearings with Aftermarket Bearings which included new ABS Sensors of course, the ABS light would pop on after so many miles of being driven. After hooking up to a scanner, for some reason the front sensors were reading a different speed then the rear sensor. Replaced the Bearings with aftermarket again, and the exact same issue. Went and got O.E. bearings and that fixed the ABS problem. I didn't get it all. How that could be?!?! They were for a Hummer H2, they Mounted up correctly, plugged in just fine, and yet wasn't reading right. Easy enough to replace, but still a big waste of time. That was a strange one.
There's no Clear ABS codes on ABS systems like on OBDII systems. They will clear themselves when the problem is fixed! If your ABS light is ON, your ABS system is disabled!!! I would get it fixed, if your ABS system just sits there, you'll have other issues later on from the system on being used and just sitting there. Then you could have a quite costly repair later on. A Sensor is pretty cheap generally. Just about everything else is not.
Does the ABS light come on with the key, stay on a few seconds and go out, then come on when you start to move? Or does the light come on and stay on without moving the truck? If the light comes opn when you start to move it is a sensor output problem - sometimes a bad sensor, sometimes a bad "tone ring" and sometimes just a dirty ring.
If the light comes on and stays on without moving, you have a bad circuit - either an open or a short - could be a failed sensor or a broken/pinched/disconnected cable.
You need to check the codes to know which wheel. I believe there is a way to test with a ameter and a jumper wire - check the shop manual for details.
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