VOLVO
CEM-1A5A - Communication with the rear electronic module (REM). Signal missing
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–)
What does this fault code mean?
The central electronic module (CEM) has lost communication with the rear electronic module (REM) and sets this code. The fault lies in the communication, not in the CEM, so the CEM should not be replaced. The REM controls, among other things, the rear door locks and windows, the trunk release, the rear window heater and the fuel gauge, so several functions at the back of the car can be affected.
Possible causes
- The REM is not getting power
- The ground wire to the REM is broken
- Contact resistance in the connections
- Broken CAN wiring to the REM
- Wrong REM for this car, for example a used module with different software or hardware
- A blown fuse inside the REM
What you can do
- 1Test the rear fog lamp with the switch on the dashboard. If it does not light, the supply to the REM may be broken
- 2Check the REM fuse. If it has blown, replace it once. If it blows again, use a multimeter to check the wire after it has no contact with ground.
- 3Check that the connector to the REM is seated and not corroded, chafed or damaged
- 4Check that the ground wire between the REM and the body is tight and clean. Use a multimeter to check it has no break
- 5After the work, clear the code and check that the rear doors and rear window work. If the code returns, read the module ID with a diagnostic tool if you have one
Symptoms you may notice5
- Rear door locking and unlocking does not work
- The trunk lid does not unlock
- The power windows in the rear doors do not work
- The rear window heater does not work
- The fuel gauge reads minimum although the tank holds fuel
General guidance for car owners. Diagnosis on the car can point to a different cause.