ABS Sensor Buying Guide
Last updated: 24 April 2026
The ABS sensor (wheel speed sensor) continuously monitors the rotational speed of each wheel and sends data to the ABS and traction control modules, allowing the system to detect wheel lock-up or spin and intervene instantly. A faulty ABS sensor illuminates the ABS warning light and disables anti-lock braking — leaving you with standard braking but without the safety benefit of ABS intervention in an emergency stop.
How ABS sensors work
Each wheel hub carries an ABS sensor that reads a toothed reluctor ring rotating with the wheel. Hall-effect sensors generate a digital square-wave signal; variable-reluctance sensors generate an analogue AC waveform whose frequency increases with wheel speed. The ABS module compares the four wheel speeds several times per second — if one wheel decelerates much faster than the others, it indicates impending lock-up and the module reduces brake pressure on that wheel.
On many modern vehicles the ABS sensor also feeds data to the stability control, traction control, hill-start assist, and active suspension systems. A single failed sensor can therefore disable multiple safety functions simultaneously.
Common causes of failure
ABS sensors are exposed to road debris, water, and temperature extremes. The wiring harness near each wheel is particularly vulnerable to chafing on suspension components, corrosion at the connector, and physical damage from kerbing. The sensor itself can be damaged by a stone or by the reluctor ring being struck during an off-road incident.
Wheel bearing replacement — especially hub assembly replacement — can dislodge or damage the ABS sensor or its wiring. Always check ABS function after any wheel bearing or hub work.
- ABS warning light on
- Traction control or stability control disabled
- ABS activating at normal braking speeds (false activation)
- Speedometer reading incorrectly on some vehicles
- Fault codes P0500–P0504 range
Replacement
ABS sensor replacement is usually a simple one-bolt job, though corroded sensors can be very difficult to extract. The replacement sensor must match the wiring plug and thread pitch of the original. After replacement, clear stored fault codes and verify ABS operation by driving and allowing the system to complete its self-check. Use the registration lookup to confirm the correct sensor for each wheel position.
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ABS and ESC warning lights — wheel speed sensor diagnosis, reluctor ring checks, and replacement guide.
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Frequently Asked Questions
What are the signs of a faulty ABS sensor?
The most common sign is the ABS warning light on your dashboard, often alongside the traction control light. You may also notice the ABS engaging erratically under normal braking or your speedometer reading incorrectly.
What does an ABS sensor do and when should it be replaced?
The ABS sensor measures the speed of each wheel and feeds that data to the ABS control unit so the system can prevent the wheels locking under heavy braking. Replace it when it fails or gives an intermittent reading, as a faulty sensor disables ABS on that wheel.
How do I know which ABS sensor fits my car?
ABS sensors are vehicle-specific, and many cars use different front and rear sensors. Enter your registration above to see only the sensors confirmed to fit your make and model.
How much does ABS sensor replacement cost?
The price of an ABS sensor depends on your exact vehicle and the brand you choose. Enter your registration above to see parts confirmed to fit, then compare prices from the brands we stock on this page. Free UK delivery on orders over £99.
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