What does it mean?
C1211 is a Chassis (ABS, traction control, steering) fault code. It indicates: Wheel Speed Sensor Rear-RH Invalid/No Signal .
Symptoms
- ABS and stability control lamps light as soon as the vehicle starts moving
- ABS is fully disabled; only normal hydraulic braking remains
- The right rear wheel reads zero on the scan tool while the other three read road speed
- Brake warning lamp may join in on systems where electronic brake force distribution shuts down
- Trailer stability and hill-hold functions unavailable
- Code returns immediately after clearing, on the first drive
Likely causes
- Open or internally shorted sensor winding
- Broken conductor in the harness near the rear wheel arch or trailing arm, often after suspension work or rodent damage
- Connector unlatched, terminal backed out of its housing, or green corrosion on the pins
- Sensor pushed out of its bore, or the tip completely packed with rust scale so no signal is produced
- Missing, spun or sheared tone ring after hub, bearing or drive shaft replacement
- Missing supply voltage from the ABS module to an active sensor
How to fix it
- Compare all four wheel speeds on the scan tool while driving slowly; a flat zero on one wheel confirms a total signal loss
- Unplug the sensor and check for supply voltage at the connector on active sensor systems, typically several volts with the key on
- Measure sensor resistance and compare with the opposite side; an open or far out of range reading condemns the sensor
- Check continuity of both sensor wires back to the ABS module connector and test for shorts between them
- Remove the sensor and inspect the bore, air gap and tone ring for damage or a missing ring
- Repair the harness section at the trailing arm and reseal the connector, then retest before fitting parts
- Replace the sensor or the hub assembly that carries the encoder, then clear the code and road-test