What does it mean?
C1235 is a Chassis (ABS, traction control, steering) fault code. It indicates: ABS Wheel Speed Sensor Left Rear Input Circuit Malfunction .
Symptoms
- ABS and stability control lamps on, sometimes only after driving over rough roads
- Left rear wheel speed reading zero or jumping about on the scan tool
- Anti lock function disabled while normal braking is unchanged
- Brake warning lamp may join in where electronic brake force distribution shuts down
- Unwanted brief ABS activation at low speed before the code stores
- Fault comes and goes with suspension movement or in wet weather
Likely causes
- Chafed or broken sensor wire along the left rear trailing arm or where it crosses the axle
- Corroded connector at the left rear wheel or water in the body pass-through grommet
- Short between the two sensor wires, or a short to ground or to battery in the pair
- Open or shorted sensor winding inside the sensor itself
- Rodent damage to the loom under the vehicle or in the boot area
- Dirty sensor tip, wide air gap or a damaged tone ring on the left rear hub
- Loose or corroded terminal in the ABS module connector
How to fix it
- Compare all four wheel speed signals live while driving and identify how the left rear behaves
- Unplug the sensor and measure its resistance, then check for a short between the wires and from each wire to ground and to battery
- Check continuity of both wires back to the ABS module connector and inspect the terminals for corrosion and lost tension
- Wiggle the harness along the trailing arm and at the body grommet while watching the signal
- Remove the sensor and inspect the tip, bore, air gap and tone ring for debris and damage
- Repair the damaged harness section and reseal any connector that has taken in water
- Replace the sensor or the hub carrying the encoder only after the wiring checks out, then road-test to confirm