Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2021 Land Rover Defender 110FACTORY OEM SERVICE PROCEDURE
Diagnostic Trouble Code Index DTC: Trailer Control Module (TRM) -- Defender/L663
- Diagnostic Trouble Code Index - DTC: Trailer Control Module (TRM) (G2445144)
- Description And Operation
- Trailer Control Module (TRM)
- Notes
- DTC B1102-19: Trailer Stop Lamp - Circuit current above threshold
- DTC B1102-53: Trailer Stop Lamp - Deactivated
- DTC B12EF-19: Trailer Fog Lamp - Circuit current above threshold
- DTC B12EF-53: Trailer Fog Lamp - Deactivated
- DTC B1407-44: Trailer Module - Data memory failure
- DTC B1407-45: Trailer Module - Program memory failure
- DTC B1407-47: Trailer Module - Watchdog/Safety C failure
- DTC B14CF-19: Trailer Reverse Light - Circuit current above threshold
- DTC B14CF-53: Trailer Reverse Light - Deactivated
- DTC B14D8-19: Left Trailer position Lamp - Circuit current above threshold
- DTC B14D8-53: Left Trailer Position Lamp - Deactivated
- DTC B14DF-19: Right Trailer position Lamp - Circuit current above threshold
- DTC B14DF-53: Right Trailer Position Lamp - Deactivated
- DTC B1541-13: Trailer Socket Connection - Circuit open
- DTC B1548-23: Trailer Light Test Button - Signal stuck low
- DTC B1D08-19: Left Trailer Direction Indicator - Circuit current above threshold
- DTC B1D08-53: Left Trailer Direction Indicator - Deactivated
- DTC B1D09-19: Right Trailer Direction Indicator - Circuit current above threshold
- DTC B1D09-53: Left Trailer Direction Indicator - Deactivated
- DTC U0037-87: Vehicle Communication Bus B - Missing message
- DTC U0037-88: Vehicle Communication Bus B - Bus off
- DTC U2300-54: Central Configuration - Missing calibration
- DTC U2300-56: Central Configuration - Invalid/Incompatible configuration
- Trailer Control Module (TRM)
- Description And Operation
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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