VOLVO
CEM-DE18 - Communication with the combustion preheater module (CPM). Signal missing
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
5 modelsC30 (2007–2013), C30 Electric (2011–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
What does this fault code mean?
The central module receives no communication from the combustion preheater module (CPM), so the parking heater does not work. The cause may be a missing supply or earth to the module, contact resistance at connections, or a break in the CAN low-speed network.
Possible causes
- No voltage supply to the combustion preheater module (CPM)
- Open circuit in the earth lead to the combustion preheater module (CPM)
- Contact resistance at the connections
- Open circuit in the CAN low-speed network wiring to the combustion preheater module (CPM)
- The preheater module does not belong to this car, e.g. a used unit with other software
What you can do
- 1Check that the main fuse at the battery and the parking heater fuse in the engine compartment fuse box are intact, using the owner's manual
- 2With a multimeter, check that the wire from the fuse box to the preheater module has no break and no contact with ground or voltage
- 3Check that the earth point of the preheater module is clean and tight
- 4If you have a diagnostic tool, try to read the module ID. If it can be read, CAN communication is probably fine and the fault may be intermittent
- 5If the fault remains, have a workshop replace the preheater module if needed
Symptoms you may notice1
- The parking heater does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.