How To Diagnose A Failing Wheel Speed Sensor
When a wheel speed sensor on your vehicle fails, your vehicle will have some serious safety issues. Most likely:
- The antilock brake system (ABS) won't function
- Stability and traction control systems won't function
It can be difficult to determine whether or not your wheel speed sensor is actually faulty. There are a few steps to follow when diagnosing this issue. We'll show you how to do that.
Signs Of A Failing Wheel Speed Sensor
If one of your Toyota's wheel speed sensors fails, you may notice these signs while driving:
- Warning lights appear on the dashboard. For example, you may see the ABS warning light and/or the traction and stability control warning lights.
- In heavy braking conditions, or on slippery surfaces, you may notice that the car takes longer to stop, and that you don't hear or feel the ABS system working.
- On slippery roads, the vehicle may be harder to control. The traction and stability control systems usually will not function with a bad speed sensor.
Either the ABS or stability/traction control system failing to work as you expect is a serious safety problem. If you notice any symptoms, you need to address the problem ASAP. The source of the problem could be in the ABS control module, or in the ECU. But, most commonly, a failing wheel speed sensor is the problem.
Testing The Wheel Speed Sensor With A Multimeter
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The best way to determine whether a wheel speed sensor is bad is to test it with a multimeter. In order to perform this test, you'll need a multimeter with a resistance setting Take these steps:
- Park your Toyota on a level surface.
- Check the fuses. It’s possible that the wheel speed sensors are fine but the ABS or traction control fuse has failed. If the fuse looks blown or damaged in any other way, replace it.
- If you have access to a code reader, it may be able to tell you which sensor if faulty. So, try the reader first.
- Remove the wheel.
- Disconnect the wheel speed sensor connector.
- Find the two-pin connector that leads to the sensor. Connect it to the multimeter.
- Set the multimeter to ohms.
- Measure the resistance. It should be minimal. If the meter indicates an open condition (very high resistance) or a short, the sensor is bad.
- Next, if the sensor passes the resistance test, set the meter to measure AC voltage.
- Have a buddy manually spin the wheel hub. Have them do it as fast as possible. Watch the voltage on the multimeter. If it changes in accordance with the speed at which the wheel hub is rotating, the sensor should be fine. If there’s no change, or no voltage read, then the sensor is likely bad. (The amount of voltage produced is very minimal, and completely safe.)
- Repeat the above steps as needed with the rest of the wheel speed sensors on your Toyota.
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