VOLVO
CEM-5F4D - Diagnostic system. Too long
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 lost contact with the parking heater control unit while the heater is running, because the heater's internal diagnostics do not respond in time. The fault lies in the communication between the two control units. It shows when the heater is active and may stop it from working as it should.
Possible causes
- Contact resistance in the connections
- Open circuit in the communication wire
- Communication wire short-circuited to ground
- Communication wire short-circuited to voltage supply
What you can do
- 1Check whether the fault is limited to the heater or whether other control units also have communication problems
- 2Check the connectors in the communication wire for loose connections and corrosion
- 3Use a multimeter to check that the communication wire has no break and no contact with ground (the body) or voltage
- 4If other control units also have communication problems, a workshop should investigate them
- 5If the fault does not return after the connectors are repaired, it was probably poor contact
Symptoms you may notice2
- Poor heating in the passenger compartment
- Parking heater does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.