VOLVO
CEM-B101286 - Left Headlamp Control. Bus Signal / Message Failures. Signal invalid
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 central electronic module (CEM) sends and receives information over a LIN serial link and checks its communication with the left main headlamp control unit (LHCU). The fault code is stored when the data from that unit is incorrect. The headlamp side and height adjustment may then be wrong or stop working.
Possible causes
- Contact resistance, oxidation or loose connections in connectors or joints
- Internal fault in the left main headlamp control unit (LHCU)
What you can do
- 1Check the connector to the left headlamp for oxidation and loose connections, and gently move the wiring with the ignition on
- 2If you have a diagnostic tool, see whether the side adjustment changes in live data when you turn the steering wheel from lock to lock
- 3Clear the fault code and road test. Check that the headlamp beam is set correctly afterwards
- 4If the fault remains, have a workshop check the control unit for the left headlamp
Symptoms you may notice3
- Headlamp side adjustment does not follow the steering wheel correctly, or does not work
- Headlamp height adjustment is wrong or does not work
- Main beam with automatic high beam control does not work
What the fault can affect2
- The headlamp light range is held constant
- Side adjustment is frozen in the straight-ahead position
General guidance for car owners. Diagnosis on the car can point to a different cause.