What does it mean?
U1138 is a Network (CAN bus, module communications) fault code. It indicates: DIS AMP Unit Fan Operation Error (Fan is running although should be off) .
Symptoms
- Fan noise from behind the dash, the console or the parcel shelf that does not stop
- The fan continues to run after the ignition is switched off, sometimes for a long period
- Battery drain and a flat battery after the vehicle has been parked
- Audio or display unit becoming hot, muting or resetting
- Buzzing or rattling from the fan itself as it ages
- The code returns immediately after clearing
Likely causes
- Fan control circuit shorted to battery voltage, so the fan is powered regardless of the command
- Fan control relay or output driver stuck closed inside the unit
- Damaged or pinched wiring behind the trim where the fan harness runs
- Fan motor drawing abnormal current or giving false feedback because its bearings are worn
- Blocked air vents or a dust-clogged heat sink, so the unit stays hot and keeps calling for cooling
- Internal fault or software problem in the display and amplifier unit
- Moisture in the unit connector after a leak or a spilled drink
How to fix it
- Switch the ignition off and listen or feel for airflow to verify the complaint
- Remove the trim and check the vents and heat sink for dust and blockage, and clean them
- Unplug the fan connector and see whether the fan stops and whether the fault code changes
- Measure the fan control wire for a short to battery voltage with the connector disconnected
- Check power, ground and the connector of the display and amplifier unit for damage and moisture
- Test the fan motor separately with a controlled supply to confirm it turns freely and draws normal current
- Replace the fan if it is faulty; replace or reprogram the display and amplifier unit only when the wiring and the fan test good