What does it mean?
C1138 is a Chassis (ABS, traction control, steering) fault code. It indicates: 4WAS Circuit .
Symptoms
- Steering system warning lamp on, often with the stability control lamp
- Rear steering stops working, so the car turns and parks differently than the driver expects
- Steering feel changes noticeably at low speed or on the motorway
- Noise or a clunk from the rear axle area when manoeuvring
- Message centre shows a steering system fault
- Fault sets straight after start up and returns when cleared
Likely causes
- Rear steering actuator motor worn out or seized, drawing abnormal current
- Wiring to the rear actuator chafed or broken where it crosses the rear subframe
- Water and corrosion in the actuator or module connector under the vehicle
- Communication fault between the main and sub control units of the steering system
- Steering angle sensor not calibrated, so the system cannot reference the front wheels
- Low supply voltage or a poor ground for the steering control unit
- Internal failure of the 4WAS control unit
How to fix it
- Read all steering and chassis modules and note which faults appear first
- Inspect the rear actuator connector and harness for water, corrosion and chafing
- Measure supply voltage and ground quality at the control unit
- Check the actuator motor resistance and compare it with specification
- Verify the steering angle sensor is correctly calibrated and the wheel is centred
- Use the scan tool to command the actuator and watch the reported position change
- Replace the actuator or control unit as the tests indicate, then carry out the required calibration