VOLVO
CEM-5F4C - Undervoltage. Signal too low
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
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
- 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
- Volvo S80 (1999–2006)2003–2004All engines except: B5254T2
- Volvo V70 (2000–2008)2000–2003
- Volvo V70 (2000–2008)2004All engines except: B5254T4
- Volvo V70 XC / XC70 (2001–2007)2001–2004
- Volvo XC90 (2003–)2003–2004
What does this fault code mean?
The fault code indicates that the voltage in the car has been too low, which can be caused by a weak battery, a damaged alternator or poor contact in the control unit connections. The fault may have occurred once without showing when the car is checked. The heater then works less well.
Possible causes
- Weak battery
- Damaged alternator
- Contact resistance in the control unit connections
What you can do
- 1Check the battery condition and that the terminal clamps are secure and clean
- 2Check that the control unit connections are secure and free from corrosion
- 3If you have a diagnostic tool, read the battery voltage in live data with the engine running and check that it rises once the engine is running
- 4If no fault is found, the fault may have been temporary, so road test the car and check whether the code returns
- 5If the fault returns, a workshop should repair the alternator or the connections
Symptoms you may notice1
- Poor interior heating
General guidance for car owners. Diagnosis on the car can point to a different cause.