VOLVO
CEM-5F47 - Control unit power supply. Signal too high
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
Show models by year and engine (10)
- Volvo S60 (2001–2009)2001, 2005–2009
- Volvo S60 (2001–2009)2002All engines except: D5244T2
- Volvo S60 (2001–2009)2003All engines except: B5244S6, D5244T2
- Volvo S60 (2001–2009)2004All engines except: B5244S6, B5254T4, D5244T2
- Volvo S80 (1999–2006)1999–2002, 2005–2006
- Volvo S80 (1999–2006)2003–2004All engines except: B5254T2
- Volvo V70 (2000–2008)2000–2003, 2005–2008
- Volvo V70 (2000–2008)2004All engines except: B5254T4
- Volvo V70 XC / XC70 (2001–2007)2001–2007
- Volvo XC90 (2003–)2003–2015
What does this fault code mean?
The central electronic module (CEM) has registered that the voltage to the heater control unit has been too high. This may be because a charger or starter unit set to the wrong voltage was hooked up, or because of a fault in the alternator. The check is made with the engine running, because the charging system is then active.
Possible causes
- Defective alternator
- A charger or starter unit set to the wrong voltage is connected
- Damaged alternator
What you can do
- 1Check whether a charger or starter unit was hooked up to the battery, and that it was set to the correct voltage
- 2Clear the code and road test the car to see whether it returns
- 3If you have a diagnostic tool, read the charge voltage in live data with the engine running and check that it stays steady
- 4If the fault was a one-off, a faulty charger may have caused it, and it need not be fixed straight away
- 5Have a workshop check the alternator and charge regulator if the fault returns
Symptoms you may notice4
- Poor interior heating
- Engine does not start or starts unreliably
- Warning lights and chimes: charging warning lit or not lit
- Alternator and charge regulator: power supply problems
General guidance for car owners. Diagnosis on the car can point to a different cause.