Over sensitive ABS/No ABS

[Snoman002]

Small problem with the Bravada, and since I trust you guys so much I thought I would ask for your help.

The ABS light came on in the Bravada the other day, right before it did the ABS was WAY to sensitive, on dry tar the ABS would kick in in a stop that did not require the ABS in any way (this is the worst part). This problem has be ongoing for the last couple days. Some times the ABS light will just be on and the ABS won't work, other times the ABS light won't be on and the ABS will engage in situations where it shouldn't, and some times the ABS light will come on, and go off, in the same drive, when the light is on the ABS won't work, when it is off the ABS engages when not needed. Heck, just a few minutes ago the ABS light came on and went off a few times while just sitting at a red light, I was turning the steering wheel back and forth while on the brakes though.

I did have a broken wire from one of the wheel sensors that I fixed before, this was also apparent when turning the steering wheel, but in that situation turning the wheel a certain way would break contact on the bad wire. In that situation the ABS would NOT be active untill a new key cycle, currently the ABS will return in the SAME key cycle.

[04crewvt]

Sounds to me like you may have corrosion on the abs sensors or a bad VSS sensor we have had a couple of threads on similar problems of late.

[rlrnr53]

I,ve run into a similar problem on a K3500 at work. It has done this about three or four times, and every time the problem was the wheel bearing. The ABS would cycle at about 3 mph just before the truck would stop. The last time, we replaced the ABS module and wiring harness because we had replaced the bearing about 6 months ago. I think the reason for so many bearing/ABS failures is that the truck is mostly used for plowing snow and has a spreader mounted on it for about 5-6 months out of the year.

[Snoman002]

Hmmm, interesting. The bearing on the passenger side is an Advance Auto replacement.

This does not just cycle at slow spees though, but it does seem to be worse if turning right.

In fact that brings me to a new problem, the ABS is engaging when the brakes aren't even being pressed now. A tight right at around 5mph will cause the ABS to cycle, but if not on the brakes you can just hear the solinoids cycling.

I'm going to disconnect the right wheel here soon, I would rather the wife drive without ABS than to have her drive it the way it is now.

[purduecrew]

hmm thats interesting. dads 94 sonoma started REALLY acting up exactly as you said about a week ago, with persisting symptoms the last year or two...would a VSS sensor apply on a 94?? they had a recall on the 94 to get the ABS "reprogrammed" but dads truck has gone nuts. the back brake pads are 80%, the original ones, and the truck has 110000 miles on it...

[F9K9]

Pre '98s had absolutely horrendous brakes. When I climbed out of my '97 ZR2 to test drive the CC I would have gone through the wind shield if, I wasn't buckled in the first time I hit the brakes. You needed to start braking a 1/2 mile from where you wanted to stop[.

[purduecrew]

update:

dad went to big o to have the brakes looked at and repaired. when he went to pick the truck up, the ABS light started goin nuts and giving him all these REALLY BAD FITS. dad walked right back inside, and big o said "take it for a few days and come back if it doesnt get better. well he took it to the gm garage today and said look, big o cant figure it out, so you figure it out. turns out big o put on a NON ABS brake rotor. basically rendered dads brakes useless!! a very scary thing to think about now, as now understanding why the pedal was being held up by the ABS even in the event of an emergency stop...so anyways, make sure if you have replaced rotors, you dont have a non abs rotor...

[HenryJ]

For our trucks the sensor is inside the front hub/wheel bearing assembly. That negates installing the wrong rotor.