VOLVO
CEM-5F50 - Overheat thermostat. 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 CEM has registered that the coolant in the heater is hotter than permitted, which sets the fault code. The fault shows when the heater is active, and the overheat protection thermostat is what guards the heater against this. The cause can be air or a blocked cooling system, or a damaged pump, thermostat or temperature sensor.
Possible causes
- Air in the cooling system
- Cooling system blocked
- Damaged water pump
- Damaged overheat protection thermostat
- Damaged water temperature sensor
What you can do
- 1Read and note the code, clear it and start the heater to see whether the fault returns
- 2Check that the hoses to and from the heater are not blocked, kinked or damaged
- 3Check that the coolant level is correct and that the cooling system contains no air
- 4If you have a diagnostic tool, read the water temperature in the heater in live data while the heater runs and compare it with the engine temperature
- 5Check the connectors at the control unit and the water pump for loose connections and corrosion
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.