The ABS on these vehicles are crap. Rust builds up and pushes the sensor away from the reluctor ring, then causing the wheel speed sensor to read the rotation wrong.
Testing the wheel speed sensors
You can check the sensors yourself with a multimeter set to the mV-AC setting. Disconnect the WSS (wheel speed sensor) and connect the multimeter to the two leads in the connector to the sensor. Spin the wheel. The mV-AC output should be around 300mV for a properly working WSS. Check both.
If it is below 250mV-AC, then you have a sensor problem that could be due to excessive air gap between the sensor and the reluctor ring inside the hub. This can be cured by filing down the surface that the sensor mounts to on the hub assembly. This will tighten the air gap, increasing the output of the sensor.
The information below will show you how to troubleshoot your front ABS and determine where the problem is before you go out and buy a new hub. Here is how to troubleshoot it:
1. Remove both wheels, remove the caliper, pull the rotor, unplug the speed sensor, hook up a digital meter to the speed sensor plug, spin the hub by hand. If you don't have 300mv or more, go to step 2.
2. Remove the speed sensor screw, clean the sensor real well as well as the mating surface, reinstall and measure your voltage, if less than 300 mv go to step 3. This where most people would buy a hub... don't do it yet!
3. Remove the speed sensor again and look at the mating surface. You may not realize it at first, but the mating surface is a stainless spacer that is held to the hub with a rivet, hit the bottom of the rivet head with a chisel but don't try to cut it off, doing this will raise the rivet and you will eventually be able to grab it with vice grips and pull it out and release the spacer.
4. Stuff the sensor hole with a torn off piece of paper towel and flat file the surface to make it clean and smooth. Clean the stainless sensor and make sure that it's flat.
5. Put a little waterproof grease on the hub's sensor mounting surface and a little on the O ring that is around the speed sensor and reinstall.
6. Check your voltage *********** CAUTION.... DO NOT leave the stainless spacer out!!!!!!!!!! ********** Failure to reinstall the stainless sensor will result in the wheel sensor being too close to the reluctor wheel and it will break a tooth on the reluctor wheel and destroy the speed sensor as well. If you break just 1 tooth on the reluctor wheel, your ABS will fire on EVERY REVOLUTION of the wheel!!
Edited by Burned, 11 February 2017 - 07:55 PM.