VOLVO
TRM-CA4B - Control Module Processor B. Bus Signal / Message Failures
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 registered a fault in the messages between the module's own parts: the signal is faulty, and contact with processor B has been lost. The fault lies in the module itself, and the trailer lighting may stop working.
Possible causes
- The tow hitch control module has lost contact with its processor B
What you can do
- 1Disconnect the battery negative terminal for a while, reconnect it, and then read the fault code
- 2If the fault remains, the tow hitch control module needs replacing, which a workshop should carry out
Symptoms you may notice1
- Trailer lighting does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.