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.
Control Module
The trailer module (TRM) manages the electrical connection between the vehicle and the trailer.
The control module in the S80 is placed in the luggage compartment underneath the left side tail lamp, in V70/XC70/V60/XC60 in the luggage compartment under the floor by the left wheel housing, in S60 in the luggage compartment by the left wheel housing and in the V40 in the luggage compartment under the right side tail lamp.
The trailer module (TRM) communicates with directly connected components and with other control modules via the controller area network (CAN).
The control module monitors input and output signal through integrated diagnostics. A Diagnostic trouble code (DTC) is stored when the control module detects a fault. Any Diagnostic trouble codes (DTCs) are stored in the control module memory. The information can be read off.
An easy way to check if the control module has power and is grounded, is to switch on the ignition and the turn signal lamps when the tow hitch connector is connected to its socket. The driver information module (DIM) indicator lamp lights and the trailer turn signal lamps should flash as they do on the vehicle. The trailer's connectors, cable harness and lights must not be damaged or defective when this check is carried out.
For further information, also see (Signal specifications).
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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.