C0051
ChassisRight Rear Wheel Speed Sensor Circuit Range/Performance
Usually the first thing you notice is the ABS light coming on, sometimes with the traction control and stability lights joining the party. The car still drives and the normal brakes work fine, but the clever stuff is switched off. Behind the scenes, the ABS module has decided the signal coming from the right rear wheel speed sensor doesn't add up. The reading is jumping around or dropping out compared to what it expects, so it stops trusting that wheel and shuts the system down to be safe.
ⓘ Information only. This page provides general educational information about fault code C0051. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does C0051 mean?
C0051 is a Chassis (ABS, traction control, steering) fault code. It indicates: Right Rear Wheel Speed Sensor Circuit Range/Performance.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • ABS warning light on, often the first and only clue
- • Traction control and stability control lights on alongside it
- • Speedometer needle dropping out or reading erratically at low speed on some models
- • ABS not kicking in during hard braking, you get a normal locked-up stop instead of the usual pulsing
- • Hill-start assist or auto handbrake refusing to work on cars fitted with them
Possible causes
Causes commonly associated with C0051, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Corrosion or muck packed around the sensor tip, very common on the rear axle where salt and brake dust collect. The reading goes intermittent before it fails outright
- 2. Failed sensor itself. The rear ones live a hard life and are a known weak spot on plenty of Fords, Vauxhalls and VAGs as they pass 80,000 miles
- 3. Damaged or chafed wiring along the rear axle, particularly where the loom flexes near the trailing arm or has been nibbled by road debris
- 4. Corroded or water-filled connector at the sensor plug, classic on older cars where the seal has gone
- 5. Rusty or chipped reluctor ring on the hub. If a few teeth are crumbling away the signal goes out of range at certain speeds
- 6. Wheel bearing play on cars with the sensor built into the bearing, the air gap changes and the signal wanders
- 7. ABS module fault, rare but possible if everything else checks out clean
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Read the live wheel speed data on a proper ABS scanner and drive the car. Watch the right rear figure against the other three. If it drops to zero, spikes, or lags the others, you've found your wheel
- 2. Get the right rear off the ground and inspect the sensor and its tip. Pull it out, clean off the metallic crud, and check the air gap. A lot of these are just contamination
- 3. Wiggle-test the loom and connector with the scanner connected. If the reading flickers when you flex the wire near the trailing arm, the harness is your problem
- 4. Check the connector for green corrosion or trapped water, a regular cause on cars over ten years old
- 5. Measure the sensor with a multimeter. Active sensors should show a small voltage swing as you spin the wheel by hand. Passive types have a resistance figure, usually around 1,000 to 2,000 ohms, check against spec for your model
- 6. Spin the wheel and look at the reluctor ring through the sensor hole or behind the hub for missing or rusted teeth. Clear the code and road test once you've sorted whatever you found
Common questions about C0051
Will the ABS light from this stop me passing the MOT? +
Yes, if the light is on when the tester looks at the dash. ABS and stability warning lights are a checked item now, so an illuminated ABS light is a straight fail. Fix the sensor, clear the code, and make sure the light stays off for a few drives before you book it. If you only clear the code and the fault is still there, the light comes back and you've wasted the test fee.
What's this likely to set me back? +
Modest as ABS faults go. The sensor itself is usually £20 to £70 for a decent aftermarket part, more for a main dealer one. At an independent garage you're looking at around £80 to £150 all in for the common bolt-in type. A main dealer will charge nearer £150 to £250. The bill climbs if the sensor is seized solid and they have to fight it out, or if it's the bearing-integrated kind where the whole wheel bearing has to come off.
How do I tell whether it's the sensor, the wiring, or just dirt? +
Pull the sensor and look at the tip first. If it's caked in metallic paste and the code clears after a clean, that was your answer and it cost you nothing. If it's clean, watch the live data while you flex the wiring near the rear axle. A reading that flickers as you move the loom means a chafed wire or a dodgy connector, not the sensor. If the wiring's solid and the sensor measures out of spec on the meter, replace the sensor. Only when all three check out should you start suspecting the reluctor ring or the module.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →