VOLVO
CEM-B103C86 - 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:
9 modelsS60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V60 Cross Country (2015–), V70 (2008–), XC60 (2009–), XC70 (2008–)
What does this fault code mean?
Communication between the central electronic module (CEM) and the left main headlamp control unit (LHCU) is invalid, because messages on the LIN bus are incorrect. The fault can be due to connectors, a break in the bus, the supply or earth, or a damaged control unit.
Possible causes
- Contact resistance, oxidation or loose connections in connectors or joints
- Break in the communication bus to the left main headlamp control unit
- Break in the voltage supply or earth connection to the control unit
What you can do
- 1With the ignition on, check the connectors and wires to the left headlamp for breaks, looseness and corrosion
- 2With the ignition off, use a multimeter to check whether the earth connection to the left headlamp is intact. The wire should have contact with the body
- 3With the ignition on, check whether the supply to the left headlamp has voltage. A break in the supply gives the same symptoms
- 4Clear the fault code and road test to see whether it returns
- 5If the fault remains, have a workshop check the communication and the left headlamp control unit
Symptoms you may notice4
- Headlamp side adjustment does not follow the steering wheel correctly, or does not work
- Headlamp height adjustment is wrong or does not work
- A message appears in the information display
- Main beam with automatic high beam control does not work
What the fault can affect2
- The light range stays in 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.