VOLVO
CEM-U003788 - Extended CAN Communication Bus. 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 control module on the extended CAN network has received or sent faulty messages and shut off its communication, which is called bus-off. The fault is caused by a short circuit between the CAN wires, and it should be located before any control module is replaced. The park assist camera, blind spot system and cross traffic alert can be affected.
Possible causes
- Short circuit between the two CAN wires in the extended network
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 check the extended-network CAN wires for chafing and pinch damage, especially where they are clamped
- 3With the battery negative lead disconnected, use a multimeter to confirm the two CAN wires have no contact. Twist the harness during the test
- 4If the code returns, have a workshop with diagnostic equipment check the network. Replace the CEM only if testing shows it is faulty
Symptoms you may notice3
- Park assist camera does not work
- Blind spot monitoring (BLIS) does not function
- Cross Traffic Alert (CTA) does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.