Making sure the ABS wheel sensor is working properly, CLEAN it!!

There are many things that can cause your ABS light to come on. Some are serious, so you should never just ignore the light. But there are times when the light comes on and can be met with a simple solution. For instance, a dirty ABS wheel sensor can cause the system to trigger the ABS light during self evaluation. You'll be shocked when you see how much road gunk can accumulate on this very important sensor.
Even if your ABS light hasn't made an appearance, it's a good idea to clean the sensor. A good time to do it would be during brake pad replacement when you have the wheels off anyway.

What You'll Need:

• Ratchet wrench and sockets
• Ratchet extension
• Jack
• Jack stands
• A strong rag

Get your stuff together and you're ready to start. Remember, it's never safe to work on a car supported by a jack, use jack stands!

Begin by loosening your wheel lugs, then jack the front of the car up and rest it securely on jack stands. With the car safe, remove the wheel lugs and take the front wheels off. With the wheel off, turn the steering wheel all the way in, opposite the side your working on. For example if your working on the passenger side, turn the wheel all the way toward the drivers side.

Locate the ABS wheel sensor (Shown in the picture above). Remove the bolts that attach it to the rest of the suspension. You may also need to remove a few bolts to pull the sensor away from the vehicle for cleaning. Follow the line to see if there are more bolts. Remember not to force it or pull too hard. Then along the line theres another two 10mm bolts, that need to be removed, just follow the abs sensor line to get at them. The initial bolts on this application are pictured below.

With the sensor free, take your rag and wipe the sensor until its clean. I prefer not to use any chemicals on the sensor to avoid potential problems. If you need to, use mild soapy solution and rinse well. Reinstall the sensor in the same manner it was removed. 

Source: Autorepair