The symptoms suggest the wheel speed sensor is developing a signal that's too weak. Since speed is a factor in the strength of any signal that's developed magnetically, the symptoms will show up at lower vehicle speeds. Most commonly that is false activation when coming to a stop.
If speed does not seem to be relevant, consider a broken or stretched cable going from the wheel bearing to the body. Check any connectors too for corrosion on the terminals or that those terminals are making good contact.
The place to start is by having a mechanic read and record the stored diagnostic fault code(s). Those will indicate the circuit or system that needs further diagnosis. They never say to replace a part or that one is bad. If there's an intermittent break at a pair of connector terminals, or a stretched cable with torn wires inside, the fault code will refer to an electrical problem with that sensor. That can be detected as soon as you start the engine. If the sensor got pushed away from the tone ring, that will cause a weak signal to be developed even though electrically everything is okay. The fault code may refer to a signal dropout, or the computer might think that wheel stopped rotating in spite of its attempts to reduce braking pressure to it.
When you're not braking, the computer still insists on seeing four identical wheel speeds while you're driving on a straight road. It knows something is wrong when one wheel's speed drops to 0 mph when the other three are still reporting identical speeds.
Sunday, August 9th, 2015 AT 3:20 AM