How to Change a Wheel Speed Sensor

If you need to change a wheel speed sensor you probably have an ABS, VSC, TRAC or car with squiggly lines coming from the bottom of it light up on your dash.  Those lights can be annoying to look at each day, but what you need to understand is that light represents a dangerous situation.  The only vehicles made with wheel speed sensors are ones that have antilock brakes or stability control systems.

Wheel speed sensors are just that, a sensor that measures the speed at each wheel.  These sensors use magnets or toothed wheels to measure how quickly the wheel is turning so your car knows if one wheel is turning much more slowly or much more quickly than all the others.  One wheel slowing represents a skid while one moving more quickly represents a loss of traction under acceleration.

abs light, change a wheel speed sensorThe ABS or skid control computer uses the data from the wheel speed sensors to apply or release the brakes independently or reduce engine power to keep your car under control.  If one wheel speed sensor malfunctions then it will shut the whole system down.  Without the ABS or tractional control system functioning your car can easily start to skid or spin out.

The bad news is that wheel speed sensors can fail relatively easily.  First, wheel speed sensors have an extremely thin wire connecting the sensor to the computer.  This thin wire makes sure the signal gets from the wheel to the computer without any interference or noise but it can also break really easily. Secondly, the sensor has to be very close to the reluctor wheel or bearing to get an accurate reading.  If the gap opens up due to rust, wear or play in the bearing like the car in this video, it will read incorrectly causing the lights to come on.

You need a special scanner to read the codes from the ABS computer but they are the only way to tell which wheel speed sensor has gone bad on your vehicle.  However, once you know which sensor is the problem, replacing them is usually pretty easy.  The car in this video is about as complicated as it gets, so if you can follow this how-to video, you can probably change the bad sensor on your car!

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abs_light.jpg – By Dimarik – Licensed by Getty Images – Original Link