Any experts on ABS brakes? My friend has had a problem for sometime now.. it seems that the ABS motor will actuate when the wheels are turned slightly.. you dont even need to apply the brakes.
He had it to a service shop last summer and the code in the computer said bad wheel sensor.. they replaced it and it continued, then they told him that you need to replace the sensors in pairs. But it seems GM will sell them seperately, or at least the shop, non GM replace one sensor..

Any help is appreciated.. this vehicle will be our tow vehicle to LOTO for the Shootout..

Thanks

Dick

Dick;

Do you mean that the ABS turns on when you steer the wheels, or when you roll the wheels?? I have never heard of this problem while steering the front wheels. If you are referring to rolling the wheels, I have not heard of this problem with G.M. vehicles. I have seen it happen to some Ford models though. I have found that it is caused by a sensor failing. Most times it wont even store a code. But, you said that this truck had a code stored. Can you send me the code #?? Is the ABS light on now? Can you scan for any current codes? Remember, a 1998 truck is OBD II, the codes can not be cleared by simply disconnecting the battery as in older cars and trucks. A scanner must be connected to read and clear codes. Give me as much information as you can, I can try to help you out on this one.

Also, whoever told you that wheel speed sensors have to be replaced in pairs does not know what the hell he is talking about..

Two possible problems-I have seen both.

The wheel bearings have a slight amount of play and during braking the sensor is losing contact due to too much air gap. But most of these have the sensor as part of the bearing so you may have already replaced the bearing.

If the bearings are tight or new then it is the brain box. If you monitor the wheel speeds on a scanner as you come to a stop you will see the frt wheels drop to 0 when the rear wheel speed is still 6-7 mph-this is why the ABS activates. If the bearings are good it needs a brain

checkmate454mag,

Thanks for the reply!! It is my buddies truck. Last year we drove to Loto with it and when you applied the brakes the ABS motor would run. It was intermittent. Well I talked to him about using his truck this year and he tells me when the truck is at slow speed and you turn the steering wheel with no brakes applied the ABS motor runs.. I said "What??"
Last year he took it to some garage. They read the code and it told them "bad sensor".. so $600 later they bring the truck back and he drives it.. same deal.. ABS motor runs when you apply the brakes.. not sure if the steering wheel had to be turned or not. So the guy says let me keep it here and check.. then he comes up with the change in pairs story.. I figured if that was true they would sell them in pairs.. go figure. I figured they didnt know what they were talking about.
I am thinking that by turning the steering wheel a wire is shorting out and turning on the ABS motor. I have not looked at it so I cant tell. Any clues as why that motor would run without the brakes being applied?

I sure appreciate the help..he has been pulling his hair out. and driving with some dangerous brakes..

Dick

I have been through the WHOLE THING !!!!!!!!!!! Trust me when I say this,,, disconnect the ABS and pull the dash bulb !!!! It's not worth the hassle !!!!!!!!!

We have driven without ABS for years, you wont miss it !!!!!!!!
Disconnecting it reverts the truck back to regular brakes, and wont cause anyproblems.

insptech,
Thanks for the reply!! He has had one side replaced and you are correct the sensor is in the bearing. But this thing goes off without the foot on the brake.. just by turning the steering wheel a little bit?? Does that ring a clue. I told him we need to go to Auto Zone and use there scan tool. He wants to fix it right, but is afraid people will just change parts till the whole truck is new again.. you know the drill ,, diagnose by replacement..
I will have him check your suggestion out.. any knowledge he has will help him when talking to a mechanic..

Thanks.

Dick

obnoxus,
Thats what I told him to do. But he would like to fix it right.. but if there is a problem with this year and make of vehicle.. then I can see the disconnect theory, but I havent heard of that many problems, with them. But then I am driving a new 1989 Blazer that I just built..the anti locks work pretty good on that one.. pump pump pump..

Thanks

Dick

Dick;

I just looked to see if there are any technical service bulletins on this one, and of course none came up. I have never seen a problem like this one. Turning the steering wheel makes the ABS pump activate!!! THATS BIZZARE!! There are no wires in the column that are in the ABS circuit, with the exception of the brake light switch, which is not actually in the column but it is pretty close to it. I don't think that can cause the problem you have. I have the wiring diagram for the circuit. I tried to attach it here on the board, but it came out to small to read. I will send it to you directly. Try to get me any stored codes. I can get any information that you need on this. Good Luck.

If it is doing it with the brakes off I wonder if the brake pedal switch for the ABS is stuck on?? Thsi would tell the unit that the brakes were applied and when you turn the wheel speeds are different-voila ABS unit activates. You need to check it with a scanner while operating.

P.S. It may not set codes-the system may think it's fine.

i work at a chevrolet dealership, and found when that happens it is usually the front hub on the right side that causes the problem. now dont get me wrong i have seen the other side bad but usually the right hub bearing assembly