VOLVO
CEM-B101C88 - Right Headlamp Control. Bus Signal / Message Failures. Bus off
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 fault concerns communication with the right main headlamp control unit (RHCU). The fault code is stored when the LIN bus is shorted to voltage or earth, which can make the right headlamp adjustment wrong or stop it working.
Possible causes
- LIN bus shorted to voltage or earth
- Damaged right main headlamp control unit (RHCU)
What you can do
- 1Check that the wiring to the right headlamp has no chafing or pinching, especially at seals and body edges
- 2With the ignition off, use a multimeter to check whether the LIN wire to the right headlamp has contact with earth (the body) or voltage
- 3Check that the connectors are dry and secure
- 4Clear the fault code and road test to see whether it returns
- 5If the fault remains, have a workshop isolate the bus and find which part is interfering with it
Symptoms you may notice3
- Side adjustment of the right headlamp does not follow the steering wheel correctly, or does not work
- Height adjustment of the right headlamp is wrong or does not work
- Main beam with automatic high beam control does not work
What the fault can affect2
- The right headlamp's light range is used as a fixed setting
- Side adjustment freezes in the straight-ahead position
General guidance for car owners. Diagnosis on the car can point to a different cause.