Diagnostic trouble code (DTC) information CEM-1A5A

Condition 

Fig 1: Identifying Central Electronic Module (CEM)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The diagnostic trouble code (DTC) is stored if the central electronic module (CEM) registers that communication with the rear electronic module (REM) is not operating.

The diagnostic trouble code (DTC) can be diagnosed when the ignition has been on for more than 10 seconds.

Substitute Value 

• None.

Possible Source 

• No power supply to rear electronic module (REM)
• Open-circuit in the ground lead for the rear electronic module (REM)
• Contact resistance in the terminals
• Open-circuit in the wiring for the CAN low speed network to the rear electronic module (REM)
• The rear electronic module (REM) is not intended for this vehicle (for example a used control module with different software/hardware).

HINT: If several diagnostic trouble codes (DTCs) are stored in the central electronic module (CEM) for communication faults with other control modules in the low speed network, this indicates a common fault in the controller area network (CAN). See the relevant wiring diagram. 

Fault symptom[s] 

• The fuel gauge indicates zero even though there is fuel in the tank.
• Rear demist does not operate.
• Retractable headrest not operating.
• The central locking system does not function at all.
• No unlocking of the trunk lid.