VOLVO
CEM-U001800 - Medium Speed CAN Communication Bus (-) shorted to Bus (+). General Failure Information. No sub type information
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 code means that the two wires in the medium-speed CAN bus are short-circuited to each other. The control modules in the car then cannot send their messages as normal, and communication on the network breaks down or is seriously disturbed. Functions linked to the bus, such as instruments, central locking and climate control, may stop working.
Possible causes
- Chafed or pinched wiring lets the two MS-CAN wires touch each other
What you can do
- 1Read and clear the fault codes in all control modules, road test the car and note whether the code comes back
- 2Switch the ignition off and inspect the MS-CAN wiring for chafing and pinch damage, especially where the wires lie close together
- 3With the battery negative lead disconnected, use a multimeter to check the two wires for contact with each other. Twist the harness during the test
- 4If the code returns, have a workshop with diagnostic equipment check the bus. Replace the CEM only if testing shows it is faulty
Symptoms you may notice4
- Instrument or button lighting does not work
- Gauges in the instrument panel do not work properly
- Central locking cannot lock or unlock the car
- Temperature control and air conditioning do not work
General guidance for car owners. Diagnosis on the car can point to a different cause.