What does it mean?
C1406 is a Chassis (ABS, traction control, steering) fault code. It indicates: Open or Short in Front Speed Sensor LH Circuit .
Symptoms
- ABS, traction and stability warning lamps on, with the systems switched off
- Left front wheel speed reads zero at all speeds in live data
- ABS may engage briefly at very low speed before shutting down
- Cruise control and hill start assist unavailable
- The fault stays present rather than coming and going, when the circuit is fully open or shorted
Likely causes
- Open winding inside the left front wheel speed sensor, or an internally shorted sensor
- Sensor wiring cut, chafed or stretched where it runs along the strut and steering knuckle
- Short to ground where the harness contacts the suspension or a brake line bracket
- Corroded connector in the wheel arch with water sitting in the housing
- Terminal pushed out of the connector so the circuit reads open
- Damage caused during a recent brake, hub or suspension repair
- Wiring damage at the module connector or a broken pin
How to fix it
- Measure the sensor resistance at the wheel-end connector and compare it with the specification for the sensor type
- Check the circuit from the module connector for open, short to ground and short to voltage with the sensor disconnected
- Inspect the full harness run from the wheel arch to the bulkhead for cuts, stretch marks and chafe points
- Open the connector and check for water, corrosion and terminals that have backed out
- Compare the readings with the opposite front corner to establish what is normal for the vehicle
- Repair the damaged harness section and reseal the connector properly
- Replace the sensor when it measures open or shorted internally, then verify all four wheel speeds during a road test