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, but can be met with a simple solution. For instance, a dirty ABS wheel sensor can cause the system to trigger the ABS light during your ABS computer's self evaluation cycle. You'll be shocked when you see how much road gunk can accumulate on this very important sensor. This sensor is also used in some traction control systems, so if you've got a traction control, or anti-skid warning illuminated you might find that cleaning the ABS sensors will remedy this, as well.
Even if your ABS light hasn't made an appearance, it's a good idea to clean the sensors. A good time to do it would be during brake pad replacement when you have the wheels off anyway. At this point it's a 10-minute job rather than an hour or two.
Removing the Wheel and Safely Supporting the Vehicle
Begin by loosening your wheel lugs (always do this while the car is still on the ground - for safety and for better leverage), then jack the front of the car up and rest it securely on jack stands. Always be sure your car is supported securely. A wobbly car or truck can lead to a serious injury or damage to the vehicle. There's no reason to take chances when you're working underneath an elevated car. 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 you're working on the passenger side, turn the wheel all the way toward the driver's side. This will give you easier access to the ABS parts both visually and in terms of your reach.
Remove the Wheel Sensor
Locate the ABS wheel sensor. Remove the bolts that attach it to the rest of the suspension. You may also need to remove a few bolts that attach the wiring to the car's frame or suspension, to pull the sensor away from the vehicle for cleaning. Follow the line and/or wiring harness to see if there are more bolts. Remember not to force it or pull too hard. Then along the line there's 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. Different vehicles are set up differently, but the idea is the same in most cases. The important thing to remember is never force anything to move. If you're removed all of the bolts and other attachment stuff you should be able to pull the sensor away with no effort at all.
Cleaning the ABS Sensor
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. The ABS sensors are precision instruments in a crude environment. They're tough enough to hang off the brakes of a very fast moving vehicle, but one good knock and they could be damaged beyond repair. Keep this in mind when working with these sensors, They're tough, but a little car taken while you service the antilock braking system along the way can save you from another costly repair added to the brake service.
To finish up the job, reinstall the sensor in the same manner it was removed, taking care to install the sensors in exactly the same manner as they were removed. Don't skip the step of reattaching the line or wiring to those mounting points. They may seem like they don't matter, but it can get very expensive if you make a bad decision.
*Don't be discouraged if your ABS light doesn't turn off right away. It may take up to a few days for the system to reanalyze itself and reset fully.
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