Diagnostic trouble code (DTC) information CEM-5F31

Condition 

Fig 1: Identifying Engine Coolant Temperature Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The central electronic module (HEM) checks the communication with the combustion preheater module (CPM).

If Central electronic module (HEM) registers open circuit or short-circuiting to voltage on the circuit for the water temperature sensor, the diagnostic trouble code is generated.

The diagnostic trouble code (DTC) can be diagnosed when the heater is activated.

Substitute Value 

• None.

Possible Source 

• Open-circuit in the signal cable.
• Short-circuit to supply voltage in the signal cable
• Damaged engine coolant temperature (ECT) sensor.

Fault symptom[s] 

• Poor heating in the passenger compartment.