The ABS sensor is the wheel speed sensor that feeds data to the anti-lock braking system. While technically the same component as wheel speed sensors used for traction control and stability systems, the ABS sensor is critical to safe vehicle operation when braking hard. ## ABS Sensor Function The ABS sensor detects wheel rotation speed and sends this data to the ABS control module hundreds of times per second. During braking, if one wheel decelerates faster than the others, the module recognises impending wheel lock and pulses the brake pressure to that wheel. Each wheel has its own ABS sensor, and the system continuously monitors all four wheels simultaneously. This allows the system to respond to changing conditions at any wheel independently. Modern ABS systems use sophisticated algorithms that can detect the difference between a wheel about to lock and normal heavy braking. This prevents unnecessary intervention while maximising braking effectiveness. The ABS control module can detect sensor faults and disable the system if any sensor provides unreasonable data. This prevents the system from acting on faulty information and potentially making braking worse. ## Diagnosing ABS Sensor Problems An illuminated ABS warning light is the most common symptom of sensor problems. The light may appear alongside the traction control and stability warning lights, as these systems share the same sensor data. Diagnostic equipment reads fault codes from the ABS module, identifying which sensor is faulty and whether the problem is in the sensor itself, the wiring, or the reluctor ring. Codes specify the affected circuit and the nature of the fault. Visually inspecting the sensor and reluctor ring is the first diagnostic step. The sensor tip should be clean and undamaged, and the reluctor ring teeth should be intact and free from debris. Metal filings accumulating on the sensor tip can cause intermittent faults. Resistance testing with a multimeter checks sensor health against the manufacturer's specification. Most sensors have a resistance between 200 and 2000 ohms depending on type. Open circuit or short circuit indicates failure. ## ABS Sensor Replacement ABS sensors are mounted in the wheel hub or on the steering knuckle, positioned with a small air gap from the reluctor ring on the wheel hub. Replacement requires removing the wheel and sometimes the brake caliper. The sensor is typically held by a single bolt and is unplugged from the wiring harness. The new sensor must be inserted with the correct orientation and the air gap set to the manufacturer's specification, typically 0.5-1.5mm. After replacement, the ABS system should be tested by performing an ABS activation at low speed in a safe location. Most modern systems also require the sensor signal to be calibrated through the diagnostic system. ## Frequently Asked Questions **Is it safe to drive with a bad ABS sensor?** The vehicle remains drivable without ABS, but emergency braking will cause wheel lock. Without ABS, you must use threshold braking technique manually. Also, traction control and stability control may be disabled, reducing overall safety. **Can I replace just the sensor or do I need the whole hub?** In most vehicles, the ABS sensor is a separate component that can be replaced individually. Some vehicles have sensors integrated into the wheel hub bearing, requiring hub replacement when the sensor fails. **Why do ABS sensors fail?** ABS sensors fail from accumulated road salt and moisture corrosion, physical damage from road debris, wire harness chafing, and natural wear of the magnetic elements. Vehicles driven in winter conditions are particularly susceptible.

Official Resources: GOV.UK Check Vehicle Tax | GOV.UK Vehicle Tax | DVLA Online | MOT Check

Frequently Asked Questions

Q: How much is car tax (VED) in the UK 2026?
Car tax rates in the UK depend on your vehicle's CO2 emissions and list price. Standard rates start from £190 per year for petrol and diesel cars, with zero-rated VED for EVs. First-year rates vary from £0 to £2,605 depending on emissions. Additional premiums apply for vehicles over £40,000.

Q: How do I check if my car is taxed online?
You can check your vehicle's tax status for free on the Gov.uk website at gov.uk/check-vehicle-tax. You'll need your vehicle's registration number (number plate). You can also check via the Motor Insurance Database to verify road tax and insurance status simultaneously.

Q: Can I get a refund on car tax if I sell my vehicle?
Yes — if you sell or scrap your vehicle, you can claim a refund on any full months of remaining road tax. Contact DVLA with the V11 reminder letter or apply online at gov.uk. Refunds are usually processed within 4-6 weeks.

Q: Is road tax refund available when transferring ownership?
No — road tax does not transfer with the vehicle. When you sell your car, the tax is automatically cancelled and any remaining months are refunded to you by DVLA. The new owner must tax the vehicle immediately. As a buyer, always verify the vehicle's tax status before purchasing. Related: UK Car Anti-Lock Brakes Guide 2026 | UK Car Brake Force Distribution Guide 2026 | UK Car Steering Angle Sensor Guide 2026 | UK Car Yaw Rate Sensor Guide 2026.

Q: What is the luxury car tax threshold in the UK 2026?
The additional rate for vehicles over £40,000 (list price) adds £410 per year to standard VED rates for years 2-6 of registration. This surcharge brings the annual cost for high-emission vehicles over £40,000 to around £600-690 per year. Pure EVs under £40,000 pay zero VED.