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 manages the electrical connection between the vehicle and the trailer.
The control module is located in the cargo compartment, behind the right wheel arch.
The trailer module communicates with directly connected components and with other control modules via the controller area network .
The control module checks the input and output signals through an integrated diagnostic system. A diagnostic trouble code is stored if the control module detects a fault. Any diagnostic trouble codes are stored in the control module memory. The data can be read off using VIDA (Volvo scan tool).
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 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 SIGNALS .
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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.