VOLVO
CEM-U004400 - Extended CAN Communication Bus (-) High. 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 negative (high) wire in the extended CAN network has contact with voltage. The network is the part where the control modules for the park assist camera, blind spot system and cross traffic alert talk to the rest of the car. A wire lying against voltage disturbs the communication, and the systems may stop working.
Possible causes
- A chafed spot in the wiring, or a pinched wire, lets the negative extended-network wire touch voltage
What you can do
- 1Read and note the fault codes in the control modules, clear them and road test the car
- 2Switch the ignition off and look for chafing, pinch damage and loose or corroded connectors in the extended-network wiring
- 3Use a multimeter to confirm the negative wire has no contact with voltage. Twist and wiggle the wiring during the test
- 4If the fault remains, have a workshop with diagnostic equipment measure the voltage. Replace a control module only once testing has shown 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.