What does it mean?
C1236 is a Chassis (ABS, traction control, steering) fault code. It indicates: Wheel Speed Sensor Rear RH Tone Ring Missing Tooth Fault .
Symptoms
- ABS and stability lamps that appear after a short drive rather than at key-on
- Brief unwanted ABS activation or a snatch at the very end of a low speed stop
- Traction and stability control switched off after the fault stores
- Code clears but comes straight back on the next drive
- Possible bearing noise from the right rear corner if the bearing is also worn
Likely causes
- Broken or chipped tooth on the right rear tone ring
- Rust building up under and between the teeth, distorting the signal at one point of the rotation
- Ring damaged or knocked out of true during hub, bearing or brake work
- Magnetic encoder ring in the bearing seal scored, contaminated with grease or partly demagnetised
- Stone chips, mud or metal debris packed into the tooth gaps
- Wrong hub or ring fitted with a different number of teeth
- Wheel bearing play changing the sensor gap at one point per turn
How to fix it
- Graph the right rear wheel speed at low road speed and look for a repeating dip once per wheel revolution
- Raise the wheel, remove the sensor and turn the hub slowly while inspecting each tooth of the ring
- Clean rust and packed dirt from the tooth gaps and confirm the ring is fully seated
- On sealed bearings, inspect the magnetic encoder for damage and compare the signal amplitude with the opposite wheel
- Verify the tooth count matches the other side and the specification
- Check the wheel bearing for play, roughness and noise
- Renew the tone ring or hub assembly, then confirm a smooth, even wheel speed trace on a road test