What does fault code CEM-DE29 mean?

Diagnostic fault code details for CEM-DE29 (Volvo C30 (2007–2013), Volvo C30 Electric (2011–2013), Volvo C70 (2006–2013)). Repair service at OBD Tuning.

VOLVO

CEM-DE29 - Communication with the climate control module (CCM). Signal missing

System

Central Electronic Module (CEM)

Volvo models this fault code applies to

Applies to the following models:

5 models

C30 (2007–2013), C30 Electric (2011–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)

Show models by year and engine (5)

What does this fault code mean?

The central module receives no communication from the climate control module (CCM). The climate system may then stop working completely, or keep working for a few minutes after the key is removed. The cause may be a missing supply, a break in the earth wire, contact resistance at connections, or a break in the CAN wiring.

Possible causes

No voltage supply to the climate control module (CCM)
Open circuit in the earth lead to the climate control module (CCM)
Contact resistance at the connections
Open circuit in the CAN low-speed network wiring to the climate control module (CCM)
The climate module does not belong to this car, e.g. a used unit with other software
Several fault codes for communication with other modules on the low-speed network point to a common fault on the CAN network

What you can do

1Switch on the ignition and the climate system. The fan should blow and its speed should be adjustable. If not, the module is missing its supply
2Check the fuses for the central module in the engine compartment fuse box, using the owner's manual
3Check that the earth wire to the climate control module and its earth point are clean and tight
4If you have a diagnostic tool, try to read the climate control module ID. If it can be read, CAN communication is probably fine
5If the fault remains, have a workshop check the infotainment relay in the central module. If the relay cannot be activated, the central module may need replacing

Symptoms you may notice3

The climate control system does not work at all
The climate control system keeps working after the key is removed
The function button does not work

General guidance for car owners. Diagnosis on the car can point to a different cause.