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ABS, TCS OFF, Service Stabilitrac Overview

Fix ABS, TCS OFF, Service Stabilitrac issues on GM vehicles

I’m not aware of any other car maker besides GM that’s had so many ABS, TCS OFF, Service Stabilitrac issues. It would be nice if there were a single common link to all of these problems, but GM has managed to screw up in every possible way.

Depending on the year, make and model, your ABS, TCS OFF, Service Stabilitrac issues could be cause by rust, broken wires, software bugs, fragile wiring harness, faulty steering angle sensors or, get this, metallic particles picked up from the road.

ABS, TCS OFF, Service Stabilitrac symptoms

Owners may complain of ABS activating at low speeds on dry pavement. You may or may not see an ABS warning light and you might even discover there are no trouble codes stores. Or you may have a lit ABS and TRAC OFF warning light.

In other cases you may experience a loss of power, jerking, or a feeling like your engine is misfiring as the traction light flickers. Still, in other cases you might see a Service Stabilitrac message on the driver information panel.

What causes the ABS to activate at low speeds

ABS activates when it thinks it sees one wheel starting to lock up. But why would this happen on dry pavement? Seven possibilities: chipped tone ring, improper air gap between the sensor and the tone ring, debris buildup on the tone ring, faulty speed sensor, break in wheel speed wiring harness, chaffing/shorting in the wheel speed wiring harness or faulty software.

Service stability can also be caused by a faulty steering angle sensor

Chipped tone ring

A chipped or missing tooth on the tone ring will cause a dropout that makes the ABS brakes think the that wheel has locked up. The only fix is a replacement tone ring.

ABS activation at slow speeds

Broken tone ring tooth

Improper air gap between the sensor and the tone ring caused by rust jacking

GM designed a tone ring inside the wheel hub assembly. But they mounted the wheel speed sensor externally, where it is exposed to the elements. Over time, water seeps under the wheel speed sensor flange and corrodes the mounting surface. As the rust and corrosion builds, it lifts the sensor farther away from the tone ring. This is referred to as “rust jacking.” The increased gap and the use of a passive style sensor results in lower AC voltage and low speeds, especially when coming to a stop at less than 5-mph. The increased gap and lower voltage triggers false ABS operation. The fix is to remove the old sensor, clean off the corrosion, coat the newly cleaned surface with a rust inhibiting grease and install a new sensor and flange.

false abs activation

False ABS activation caused by corrosion and rust jacking.

Debris buildup on the tone ring

Rust buildup on the tone ring is common in areas where road salt is used and the tone ring is exposed to the elements. The layer of rust interferes with the sensor gap and causes false ABS activation. The fix is to remove the surface rust using non-metallic scrubbing pads.

Debris buildup can also occur immediately follow a brake job where the rotors were machined on the vehicle and where the technician did not properly clean the tone ring after the machining process. It’s the metallic debris from machining that causes the false ABS activation.

©, 2019 Rick Muscoplat

 

Posted on by Rick Muscoplat

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