VOLVO
CEM-B123387 - Interior Motion Sensor "B". Bus Signal / Message Failures. Missing message
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
4 modelsS60 (2011–), V60 (2011–), V60 Cross Country (2015–), XC60 (2009–)
Show models by year and engine (4)
What does this fault code mean?
The interior motion sensor (MMS) communicates with the CEM over the LIN bus. The fault is stored when communication with the motion sensor is missing for too long. The causes are an open circuit in the supply or earth to the sensor, contact resistance in the connections, or the sensor having stopped working.
Possible causes
- Open circuit in the power supply to the motion sensor
- Open circuit in the earth wire to the motion sensor
- Contact resistance in the connections
- The motion sensor has stopped working
What you can do
- 1Check that the fuses are intact
- 2Activate the alarm and see whether the motion sensor responds, then clear the fault code and road test
- 3Check the supply and earth to the interior motion sensor for breaks and contact resistance in the connectors
- 4Check the wire between the motion sensor and the CEM for chafing and loose connectors
- 5If the fault remains after these checks, have a workshop with diagnostic equipment check the motion sensor and replace it if needed
Symptoms you may notice2
- The alarm does not respond when the sensor should trigger it
- A message appears in the text display
General guidance for car owners. Diagnosis on the car can point to a different cause.