Question: 2001 Chevy Impala and am having problems with it off and on. It starts with the anti lock brakes activating on there own and sometimes it stops. Other times it will kick on the traction system and the ABS light will come on. You can feel the brakes dragging when it happens. Doesn't happen all the time but seems to be happening more often now. The wheel bearings are tight.
Use to be it did it when steering wheel was turned hard. Now it does it just by going down the road. I can disable the traction control and it will still do it. Doesn't matter if I am braking or not, and a lot of times starts when I am backing up. Mechanic just cleaned the connections for the sensors at the wheel bearings and checked the wiring to see if they had become stretched or broken.
Answer: This and many other vehicles have bad problems with the wheel speed sensor harnesses. The wires will break inside the wire insulation. This normally happens where the wire is bending and flexes with the suspension travel. It can be extremely difficult to diagnose this condition. You can try and OHM test the sensor wires between the sensors and the ABS control module (EBCM). The easiest thing to do is to replace the harness. They can be purchased from your local dealer. Another thing to check is the large wire harness that runs next to the A/C dryer assembly. The dryer is the large aluminum cylinder on the drivers side near the radiator. This harness can make contact with the dryer or the pipes attached to it and cut the wires. The wires that normally get damaged are the ABS speed sensor wires.