Anti-lock Brake Systems Troubleshooting Guide
Action to be taken: 1) Safely raise and support the vehicle. 2) Disconnect the front wheel speed sensors from their harness and frame. 3) With a digital volt-meter attached to the terminals of each wheel speed sensor connector, rotate the wheel in a clockwise direction approximately one revolution per second. The minimum reading on the meter should be at least 350 ACmV’s. If the reading is less than that, remove the sensor. 4) Plug the sensor bore to prevent debris from falling into the hub.
5) With a wire brush, sandpaper, or another suitable cleaning device, thoroughly clean the speed sensor mounting surface. 
Install the original sensor or replacement sensor in the hub and make certain it is seated flush against the hub. 9) Re-check the sensor voltage while rotating the wheel as previously described. The voltage should read a minimum of 350 ACmV’s. LOSS OF EBCM GROUND GM advises that electronic brake control modules (EBCM) are being replaced needlessly due to poor ground circuits.
