ABS Speed SensorsWhat is an ABS wheel speed sensor?
An anti-lock braking system (ABS) wheel speed sensor measures a vehicle’s wheel speed and transmits that data to the ABS control module to ensure all wheels move at the same speed.How does an ABS speed sensor work?
Most speed sensors are part of the vehicle’s wheel hub. The sensor consists of a magnet and an electromagnetic coil. As the wheel rotates, it creates a magnetic field around the sensor. The coil registers the speed and transmits the data to the ABS control module.What role does an ABS wheel speed sensor play in an anti-lock braking system?
A modern vehicle equipped with anti-lock brakes relies on the car’s wheel speed sensors to monitor the vehicle’s condition. The wheel speed sensors relay the wheel’s speed to the ABS control module. Based on multiple data points, the ABS control module will determine if a wheel is nearing the point when the wheel might lock up and start to skid. If so, the ABS will rapidly pulse the brake fluid pressure to slow down or stop the vehicle safely.How do you know if your ABS speed sensor is bad?
Wheel sensors are critical components in the ABS. If one fails, a check engine light (CEL) or the ABS icon will light up. In addition, you can use an onboard diagnostics (OBD) code reader to determine if the wheel sensor is at fault. Drivers may also notice a pulsating brake pedal and difficulty stopping.
After removing a wheel sensor from the vehicle, check the sensor with a multimeter. Consult a service manual to verify how to measure the sensor’s resistance and compare it to the manual’s specifications.How do you replace a wheel ABS speed sensor?
A wheel sensor is relatively easy to replace with the proper tools. Here are the basic steps, but confirm the specific steps for your vehicle as indicated by the service manual.
- Disconnect the negative battery cable.
- Safely jack up the car and remove the wheel with the defective sensor.
- Remove the sensor retaining car bolt. It often is located at the bottom of the wheel assembly. You should spray the bolt with a penetrant to loosen it.
- Remove the sensor and follow the sensor’s wire harness to a connector. Disconnect the connector from the balance of the wiring harness.
- Clean the sensor mounting area with brake cleaner and use a clean rag to remove debris.
- Replace the wheel speed sensor and reconnect the wire cable to the harness, using clips or brackets to keep the wiring snug.
- Replace the wheel and lower the car to the ground.
- Reconnect the battery and confirm that the ABS signal is no longer lit.
An ABS wheel speed sensor is a critical safety component. When it fails, it should be promptly replaced.How many wheel sensors are on a car?
Most modern vehicles have four ABS wheel sensors, one for each wheel. Some variants measure the speed via the differential or transmission. Consult a service manual to confirm the style of your vehicle.