VOLVO
CEM-DE70 - Communication with Headlamp Control Module (HCM) 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 CEM has lost contact with the headlamp control module (HCM), so the headlamps cannot be controlled as normal. The fault is most often caused by supply, earth or a connector at the HCM, or by a broken LS-CAN wire.
Possible causes
- No supply to the HCM
- Open circuit in the earth wire to the HCM
- Contact resistance in the connections
- Open circuit in the LS-CAN wires to the HCM
- The HCM does not suit the car, for example a used module with other software or hardware
What you can do
- 1Switch the headlamps on and see whether either one lights. If neither does, the fault is probably the supply or earth to the HCM
- 2Check the HCM circuit fuse in the engine bay fuse box and in the CEM. If one has blown, check its circuit for a short to earth
- 3Use a multimeter to check that the supply wire from the CEM to the HCM has no break and is not shorted to earth
- 4Check the HCM earth point for contact resistance and oxidation
- 5With a diagnostic tool, read the HCM ID. If it reads, the communication is probably fine and the fault may be intermittent
- 6Headlamps matter for safety: do not drive in the dark with faulty ones, and have a workshop repair the fault promptly
Symptoms you may notice1
- The headlamps do not work
General guidance for car owners. Diagnosis on the car can point to a different cause.