VOLVO
CEM-5F31 - Coolant temperature sensor Open circuit or short circuit to supply
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) monitors the water temperature sensor in the heater. If the circuit is broken or has contact with voltage supply, the control unit treats this as a fault and sets the code. The fault shows when the heater is active, and it causes poor heating in the passenger compartment.
Possible causes
- Open circuit in the signal wire or a short-circuit to voltage supply in it
- Open circuit in the signal ground wire
- Contact resistance in the control unit connector
- Defective water temperature sensor
What you can do
- 1Read and note the code, clear it and start the heater to see whether the fault returns
- 2If you have a diagnostic tool, read the water temperature in live data and compare it with the engine temperature once the engine is warm
- 3Check the connectors at the control unit and at the water temperature sensor for loose connections and corrosion
- 4If the heater works again after the connectors are repaired, the fault was probably poor contact
- 5Use a multimeter to check the water temperature sensor wires for breaks or contact with voltage; if they are intact and the fault remains, a workshop should replace the sensor
Symptoms you may notice1
- Poor heating in the passenger compartment
General guidance for car owners. Diagnosis on the car can point to a different cause.