Diagnostic Trouble Code Information

Condition 

Fig 1: Identifying Engine Coolant Temperature Sensor

Courtesy of VOLVO CARS CORPORATION

If the water temperature sensor circuit is short-circuited to voltage supply or if there is an open circuit, the control unit will interpret this as a fault, and diagnostic trouble code CEM-5F31 will be set.

Substitute Value 

• None.

Possible Source 

• The signal wire has an open circuit or is short-circuited to voltage supply.
• Open circuit in the signal ground wire.
• Contact resistance in control unit connector.
• Defective water temperature sensor.

Fault symptom[s] 

• Poor interior heating.