VOLVO
TRM-90D6 - Trailer electrical fault
System
Trailer Module (TRM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsC30 (2007–2013), C70 (2006–2013)
Show models by year and engine (2)
What does this fault code mean?
The tow hitch control module (TRM) has detected an external power supply from the trailer that is higher than the car's system voltage. The fault most likely comes from a trailer or caravan with its own power source. The affected output on the trailer socket is blocked, and the trailer lighting may stop working.
Possible causes
- A trailer or caravan with its own power source at a higher voltage than the car has been used
- Electrical fault in the connected trailer
What you can do
- 1Check that the trailer or caravan electrical system is not powered from its own supply, including on lighting circuits other than the rear fog lamp
- 2If the caravan has its own battery, disconnect it before the caravan is connected to the car, so the message does not return and the control module is not put at risk
- 3If the owner wants to charge the caravan battery while driving, the trailer socket needs to be changed to a modern one that supports it, which a workshop can help with
- 4Have a workshop check the trailer electrical system if the fault remains
Symptoms you may notice2
- Message in the display that the trailer needs service
- Trailer lighting does not work
What the fault can affect1
- The affected output on the trailer socket is blocked by the tow hitch control module
General guidance for car owners. Diagnosis on the car can point to a different cause.