VOLVO
CEM-U004000 - Extended CAN Communication Bus (+) Low. 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 positive (low) wire in the extended CAN network has contact with ground. The network links the park assist camera, blind spot system and cross traffic alert with the rest of the car. Ground contact on the wire disturbs the signals, and the systems on the network can then stop working.
Possible causes
- Chafed or pinched wiring lets the positive extended-network wire touch ground
What you can do
- 1Read the fault codes in all control modules, clear them and road test the car to see whether the code returns
- 2Switch the ignition off and inspect the positive wire of the extended network for chafing, pinch damage and loose connectors
- 3With the battery negative lead disconnected, use a multimeter to confirm the positive wire has no contact with the car body. Twist and wiggle wiring during the test
- 4If the code returns, have a workshop with diagnostic equipment check the voltage drop in the wires. 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.