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How to Find Out What Anti Lock Sensor Is Bad

Most modern passenger vehicles use two or more anti-lock brake sensors to determine the rotational speed of the wheels. These sensors relay wheel speed information to the ABS computer and the powertrain control module, or PCM. The ABS and PCM computers use this information to calculate when to activate the anti-lock brake system, engage the traction control, retard the ignition timing and many other actions. When a wheel sensor fails, the on-board computers cannot gather information properly. In this situation, they disable one or more of these systems until the problem is remedied.

Instructions

1

Drive your vehicle to a safe location where you can perform an isolated road test. This could be a large, empty parking lot or a remote street without pedestrians and cars. Youll need to read a scan tool while the vehicle is moving, so its important to be in a safe testing location.

2

Connect an ABS-capable scan tool to the vehicles diagnostic port and turn on the scan tool. Navigate to the ABS menu and select the Live Feed function. Your scan tool may have the Live Feed menu labeled as something different, but youll need to find the menu or setting that allows you to read the live data from the wheel speed sensors.

3

Drive the car forward and accelerate to 15 miles per hour. Glance down at the scan tool and make sure that all of the wheel speed sensors show the same 15 miles per hour reading as the speedometer inside the vehicle. If one of the sensors shows 0, Zero or N/A, then that sensor is not providing the computer with a wheel speed value.

4

Return home and park inside your garage. Turn off the engine and raise the end, front or rear, of the vehicle that has the bad wheel sensor. Support it with jack stands and chock the wheels on the opposite end. Apply the parking brake, if the opposite end is the rear of the vehicle.

5

Crawl underneath the vehicle and locate the wheel speed sensor that wasnt responding. Use a work light to inspect the wiring harness and for cuts, frays and other damage.

6

Disconnect the wheel speed sensors electrical connector and turn the ignition to the ON position. Measure the voltage at the sensors electrical connector with a digital multimeter. Look up the specified value in a service manual and compare that to the value on your digital multimeter. If the value is correct, and the wires arent frayed or damage, then the sensor is bad and must be replaced.

Posted by Unknown at 3:45 PM

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Labels: anti, bad, find, how, is, lock, out, sensor, to, what