VOLVO
CEM-B12C986 - LIN Bus "E". Bus Signal / Message Failures. Signal invalid
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsV40 (2013–), V40 Cross Country (2013–)
Show models by year and engine (2)
What does this fault code mean?
The CEM communicates with the overhead console (OHC) and the rear reading light (RRL) over the LIN bus. The fault is stored when messages on the bus become corrupt, and The fault affects the functions that are controlled from the overhead console and the rear reading light.
Possible causes
- Contact resistance, oxidation or poor contact in the connector terminals and connections
- Damaged overhead console (OHC)
- Damaged rear reading light (RRL)
What you can do
- 1Check that the fuses are intact
- 2Try the buttons for the rear reading light and the panoramic roof sunshade and note which functions do not work
- 3Check the connectors at the overhead console and the rear reading light: loose or oxidised connectors should be cleaned and pressed in
- 4Check the LIN wire between the CEM, the overhead console and the rear reading light for chafing and pinch damage
- 5If the fault remains, have a workshop with diagnostic equipment check the overhead console and the rear reading light
Symptoms you may notice2
- The electric sunshade in the panoramic roof does not work
- The lighting in the passenger compartment does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.