VOLVO
CEM-B139E01 - Main Battery Diode. General Failure Information. General electrical failure
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
8 modelsS60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V70 (2008–), XC60 (2009–), XC70 (2008–)
Show models by year and engine (17)
- Volvo S60 (2011–)2011–2012
- Volvo S60 (2011–)2013–2014Engine B5204T8, B5204T9, D5204T3, D5204T7 only · Transmission TF-80SD only
- Volvo S60 (2011–)2015Engine D5204T3, D5204T7 only · Transmission TF-80SD only
- Volvo S80 (2007–)2011
- Volvo S80 (2007–)2012, 2015Engine D5204T3 only · Transmission TF-80SD only
- Volvo S80 (2007–)2013–2014Engine D5204T3, D5204T7 only · Transmission TF-80SD only
- Volvo V40 (2013–)2013–2015
- Volvo V40 Cross Country (2013–)2013–2015
- Volvo V60 (2011–)2011
- Volvo V60 (2011–)2012Engine D5204T3 only · Transmission TF-80SD only
- Volvo V60 (2011–)2013–2014Engine B5204T8, B5204T9, D5204T3, D5204T7, D82PHEV only · Transmission TF-80SD only
- Volvo V60 (2011–)2015Engine B5204T9, D5204T3, D5204T7, D82PHEV, D87PHEV only · Transmission TF-80SD only
- Volvo V70 (2008–)2011
- Volvo V70 (2008–)2012Engine D5204T3 only · Transmission TF-80SD only
- Volvo V70 (2008–)2013–2015Engine D5204T3, D5204T7 only · Transmission TF-80SD only
- Volvo XC60 (2009–)2011
- Volvo XC70 (2008–)2011
What does this fault code mean?
This fault code only applies to cars with automatic engine start/stop. The main battery diode has a safeguarding role: when the secondary battery cannot keep up with the car's consumers during cranking, the diode makes sure the main battery contributes. The CEM monitors the diode, and the fault is stored when the voltage difference is wrong for too long.
Possible causes
- Open circuit in the wire between the main battery and the main battery diode
- Damaged battery diode
What you can do
- 1Check that the main battery is fully charged and that the fuses are intact
- 2Check the wire between the main battery and the main battery diode for breaks, loose connectors and corrosion
- 3Check the connections at the battery and at the diode: corroded or loose terminals should be cleaned and tightened
- 4If you have a diagnostic tool, compare the voltage from the main battery and the secondary battery in live data while the engine is started
- 5If the fault remains after these checks, have a workshop check and if needed replace the battery diode
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.