VOLVO
CEM-B10BE21 - Solar Sensor. General Signal Failures. Signal too low
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsV40 (2013–), V40 Cross Country (2013–)
Show models by year and engine (2)
What does this fault code mean?
The CEM monitors the signal from the sun sensor. The code is stored when the signal voltage is too low for the module to accept it. The cause may be a signal cable shorted to ground or a damaged sun sensor, and the fault usually shows up as instrument and button lighting that does not work.
Possible causes
- The signal cable to the sun sensor is short-circuited to ground
- The sun sensor is damaged
What you can do
- 1Check that the relevant fuses are intact. Their locations are in the owner's manual or on the fuse box cover
- 2Look for chafing on the sun sensor wiring, especially where it may have been pinched
- 3Check that the sun sensor connector is secure and free from corrosion
- 4If you have a diagnostic tool: follow the sun sensor value in live data and check that it changes when the light reaching the sensor changes
- 5If the fault returns with the wiring and connector in good order, have a workshop with diagnostic equipment check the sun sensor and the control module
Symptoms you may notice1
- Instrument and button lighting does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.