Originally posted here. I didn't see this in the Tech section so I thought I would post it up. If I have left anythign out please let everyone know. I have done this on several 1500, 2500 and 3500 GMC and Chevy trucks. I believe that this part of the systems is pretty universal on all chevy gmc trucks. GM 1500 2500 3500HD ABS Wheel Speed Sensor Service Or Replacement Information Instructions The compaint most commonly associated with this failure of the wheel speed sensor would be that the ABS system engages at low speed and during normal stopping or pulling into a parking spot. The problem to be fixed is rust build up between the wheel hub bearing and the wheel speed sensor plug. The build up causes just enough separation between the hub bearing and the wheel speed sensor that the wheel speed sensor loses contact with the hub reluctor ring. To repair this you need to remove wheel from the hub. Once the wheel is off, remove the brake caliper by loosening the 18mm hex head or torx head bolts at the bottom and top back of the brake caliper. (GM originally designed the brake caliper mounting bolts as torx head bolts, but they were prone to have the head strip out during removal so they redesigned them as hex head bolts) Sorry about the blurry pics, they are taken with a cell phone. This shows the bottom bolt. Once the bolts are out, use a good sized pry bar, screw driver or something you can pry with to pry the brake caliper off of the brake rotor. Be careful not to allow the brake caliper to fall with only the brake line to support them, they have been known to fail after this. Once the brake caliper is loose from the rotor, flip it upside down on the upper control arm and secure it with a bungy cord. Once this is done you can see the ABS wheel speed sensor on the top of the wheel hub bearing. Remove the alan bolt that secures the wheel speed sensor and remove the speed sensor from the hub bearing. Plug the hole on top of the hub bearing with something to keep debri from getting into the wheel hub bearing. Then use a heavy wire brush, course sand paper or wire wheel in a grinder or drill to clean the corrosion off ot the top of the wheel hub bearing. You do not want to create a concave hole in the top of the hub bearing, but you want it good and clean. Once you have cleaned the top of the hub bearing, Paint the cleaned section of the hub bearing with a LIGHT coat of rust preventing paint and allow it to dry for at leasst five minutes. Then after ensuring that the sensor plug isn't warped or distorted go ahead and reinstall the speed sensor. Trace the wiring harness for the wheel speed sensor to the plug on the main wiring harness side just above the frame and unplug it from the main harness. Run the digital volt meter across the terminals on that end of the wheel speed sensor on each side of the truck to determine proper voltage. Once connected to the wheel speed sensor, rotate the wheel hub bearing quickly. You are causing a magnetic signal that generates electiricity through the sensor, so give it a good turn. When you do that you should have a reading from the volt meter should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor and replace it. Once it is replaced, retest the voltage of at the sensor to ensure that the issue is fixed. If you still do not read at least 350 ACmV's then repeat the hub cleaning process. Once replaired and or replaced simplay reassemble the entire wheel and brake assembly in the order in which you disassembled it. Hope this helps at least a little bit.