What does it mean?
C1203 is a Chassis (ABS, traction control, steering) fault code. It indicates: Wheel Speed Sensor Front-RH Open/Short .
Symptoms
- ABS, traction and stability control lamps on and staying on from the first drive
- ABS never engages: the pedal stays firm and the wheel can lock during a hard stop
- Front right wheel speed reads zero in live data while the other channels follow road speed
- Stability control cannot brake that wheel to correct understeer or wheel spin
- The fault may be intermittent at first, appearing on rough roads or at full steering lock
Likely causes
- Sensor lead broken inside its insulation where it flexes with steering and suspension movement
- Sensor winding open or shorted internally
- Cable rubbed through against the strut, a brake line bracket or the wheel arch liner and shorting to the body
- Water and corrosion in the connector behind the arch liner, giving an open or a bridged circuit
- Terminal backed out or the connector not latched after brake, hub or suspension work on that side
- Physical damage from stone strikes, kerb impacts or a snow chain
- Fault in the ABS module input stage for the front right channel
How to fix it
- Compare all four live wheel speeds while rolling the car forward slowly to confirm the dead channel
- Inspect the front right sensor lead over its full length, particularly where it follows the strut and turns with the steering
- Disconnect the sensor connector and check for water, corrosion, loose terminals and an unlatched housing
- Measure the circuit from the ABS module connector: an open shows very high resistance, a short shows near zero or unexpected voltage
- Test the same circuit for a short to ground and to battery with the module unplugged
- Wiggle the harness with live data displayed to catch a break that only opens with movement
- Repair the wiring or connector first, then replace the sensor if it measures outside specification once the circuit is proven