VOLVO
CEM-B13DF01 - Main Battery Diode Or Relay. General Failure Information. General electrical failure
System
Central Electronic Module (CEM)
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?
This fault code only applies to cars with automatic engine start/stop. The CEM monitors the main battery relay, the main battery diode and the secondary battery relay. The fault is stored when the supply voltage to the CEM is too low on a restart after an auto stop. The causes lie in the relays, the diode, the fuse or the wiring to the secondary battery, or in a battery with poor capacity.
Possible causes
- The main battery relay has stuck in the closed position
- The secondary battery relay is damaged or has stuck in the open position
- Damaged main battery diode
- Damaged fuse for the secondary battery
- Open circuit in the wire to the secondary battery
- The secondary battery has poor capacity
What you can do
- 1Check that the fuse for the secondary battery is intact
- 2Check that the battery is fully charged and has good capacity, and that the terminals and cables are clean and intact
- 3Check the wire to the secondary battery for breaks and loose connectors
- 4If you have a diagnostic tool, check in live data what voltage the CEM sees when the engine is restarted after an auto stop
- 5If no fault is found, have a workshop check the relays and the diode and replace them if needed
Symptoms you may notice2
- The automatic start/stop function does not work while driving
- The automatic start/stop function does not work at idle
General guidance for car owners. Diagnosis on the car can point to a different cause.