VOLVO
CEM-DD21 - LIN bus 9. No communication
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
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 wiper motor module (WMM) and the rain sensor (RSM) cannot be reached over the LIN bus, even though the central module tries to communicate. The cause may be a break or short circuit in the wiring, or a damaged communication device. The rain sensor stops working, and the wipers may behave wrongly.
Possible causes
- Short circuit between the LIN wires
- Open circuit in one of the LIN wires
- Damaged communication device in a control module
- Fault in another unit on the same LIN network
What you can do
- 1Check the fuses for the wipers and the rain sensor, using the owner's manual, and replace any that are blown
- 2With a multimeter, check the wire to the wiper motor module for breaks and contact with ground
- 3Make the same check on the wire to the rain sensor
- 4If the wires are intact, have a workshop replace the wiper motor module
Symptoms you may notice2
- The rain sensor does not respond
- The windshield wipers do not work
What the fault can affect2
- The wipers may run too fast or too slow, or at the wrong interval, for a time
- The wipers may stop completely
General guidance for car owners. Diagnosis on the car can point to a different cause.