VOLVO
TRM-U1A4B8F - Control Module Processor B. Bus Signal / Message Failures. Erratic
System
Trailer Module (TRM)
Volvo models this fault code applies to
Applies to the following models:
9 modelsS60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V60 Cross Country (2015–), V70 (2008–), XC60 (2009–), XC70 (2008–)
What does this fault code mean?
The tow hitch control module (TRM) has registered an incorrect signal from its own processor B, 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 (TRM) has lost contact with its processor B
What you can do
- 1Run a functional test of the trailer lights with a working trailer connected
- 2Read the fault code again after the test to see whether it is still present
- 3Have a workshop download the latest software to the tow hitch control module
- 4If 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.