VOLVO
CEM-8FB2 - Rain sensor module (RSM). Faulty function
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 registered that the rain sensor has not been able to adapt automatically to the windscreen. The rain sensor then does not work as it should, so the wipers may not be controlled correctly in rain.
Possible causes
- Damaged rain sensor
- The rain sensor is not properly fixed to the glass
- Crack in the glass by the rain sensor
- Stone chip on the glass by the rain sensor
What you can do
- 1Clear the code and check whether it returns with the ignition on
- 2Check that the rain sensor connector is firmly seated and clean, with no contact resistance or oxidation
- 3Make sure the rain sensor is intact and fixed firmly to the windscreen
- 4Look for cracks and stone chips in the windscreen by the rain sensor
- 5If none of these is found, have a workshop replace the rain sensor
Symptoms you may notice1
- The rain sensor function does not work
What the fault can affect1
- If the fault appears a while after the rain sensor is activated, the wipers switch to the highest speed
General guidance for car owners. Diagnosis on the car can point to a different cause.