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ABS activating on light pedal pressure on dry roads

I have a 2008 Isuzu Ascender which is basically a GMC Envoy with an Isuzu name on it . While driving at times the ABS is activating under light pressure when coming to a stop on dry roads. Does not happen every time . Does not seem to matter if the car is cold or if I have been driving awhile. Every once in a great while it will aLso activate the the stability/traction control when starting from a stop which then kills the gas because it thinks the wheels are slipping I assume. About a month ago had a right front wheel bearing replaced trying to fix this issue and that did not do it so I am assuming it is one of the other three most likely . Have read on these GM vehicles (trailblazer/Envoy)there is a tendency for corrosion to build up under the wheel sensor mounting surface which then changes the “air gap” between the sensor and what it reads in the wheel bearing which can cause issues like what I’m seeing . There is no lights on the dash other than when it occasionally activates the stability /traction control which then that light flashes briefly while it kills power to the wheels and then recovers and runs normally . Any one run into issues like this ? What was the remedy . May have them clean all the mounting surfaces on the remaining sensors. When I had it looked at before there was no abnormal codes stored so i am chasing an intermittent issue. Thanks for any info .

This happened on my Chevy Avalanche but only under braking as I do not have stability control. I cleaned the sensors. Replaced a wheel bearing (the other side was already new). It did nothing.

The solution I found was to level the truck side to side by adjusting the torsion bars. Yeah, that seems strange but… when one corner sags, the opposite side carries more of the load. Under braking, that extra load means the loaded wheel rotates a slight bit faster than the less loaded wheel and the ABS sees that like the tire is about to skid so it activates the ABS. Should also work similarly with stability control.

Put the truck on a level surface. Start at the front. Measure the ride height from ground to the top of the wheel opening. Compare that to the opposite side. It should be within 1/2 inch. If it isn’t, you need to find out why. Look for a broken 1/2 a coil usually at the bottom. Same for the rear springs. Replace the spring or shim it on the low side to level it.

Remove the wheel speed sensors and inspect their mounting surfaces for rust.

When rust forms under these sensors, it causes them to become misaligned with the tone rings. This then causes the ABS to activate on dry roads when braking at slow speeds.

Tester

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This is what I was thinking too . Seems to be an issue on GM vehicles . Would this be on all 4 for this problem or will it usually be the front sensors ? One other question is when they replaced the right front bearing does the new bearing come with the new sensors attached ? If it does then I should concentrate on the other side .

No.

The wheel speed sensor is a separate component.

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Tester

Yes, most new wheel bearing do come with new sensors. Gm at least. They can be removed for several years. If you want to look at them. Then the corrosion is so bad they are fused into the holes.

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When I drove school bus every chevy van chassis , suburban and our shop chevy pickup had recurring problems with this. Usually the shop would replace a wheel speed sensor and that would fix it…for a while.

Driving with worned tires can cause that also.

The equinox I got last yr had the abs fuse removed. Of course I had an abs light. But no rumble. Till I put the fuse back in. I have changed 2 wheel bearings for noise but the rumble remains. Guess those 2 bearings were not the the sensor issue?

What is next? First killer bees, then murder hornets, now tire worms. Its just not safe to go out anymore.

W o r n e d Tires. :sunglasses:

Don’t say that you weren’t warned!
:wink:

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