What does it mean?
C1205 is a Chassis (ABS, traction control, steering) fault code. It indicates: Wheel Speed Sensor Front-RH Invalid/No Signal .
Symptoms
- ABS, traction and stability control lamps on, usually together
- Front right wheel speed shows zero in live data even though the car is moving
- ABS is inactive: the pedal is firm and the wheel can lock in an emergency stop
- Stability and traction control cannot brake that corner, so grip is lost more easily on a slippery surface
- Any function that depends on wheel speed, such as cruise control or hill-start assist, may be blocked
Likely causes
- Tone ring cracked, rusted through or spun loose so there are no clean teeth to read
- Sensor tip packed with metallic debris or brake dust
- Sensor sitting proud of its bore because of corrosion, leaving an air gap that is too wide to generate a signal
- Sensor failed internally: the circuit measures normally but no output is produced
- Wrong hub, bearing or sensor fitted with a tooth count the module does not expect
- Wheel bearing worn enough that the hub moves away from the sensor under load
- Damaged lead attenuating the signal so far that the module discards it
How to fix it
- Roll the car and watch the live wheel speeds; a channel reading zero with a healthy circuit points at the signal source, not the wiring
- Remove the sensor and clean the tip and the hub bore completely, checking for a build-up of rust behind the sensor
- Turn the wheel slowly by hand and inspect the tone ring right around for cracks, missing teeth and corrosion lifting
- Refit the sensor fully seated and confirm the air gap matches specification
- Test the sensor itself: winding resistance for a passive unit, or supply voltage and switched output for an active unit
- Check bearing play and confirm that the correct hub and sensor combination is fitted for the vehicle
- Replace the sensor if it produces no output, or the hub and bearing assembly if the tone ring is damaged, and verify all four channels on a road test