VOLVO
CEM-U000800 - High Speed 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?
On the V40 the negative wire of the high speed CAN is at supply voltage, which disturbs communication between the control modules. The engine may then have trouble starting, and driving and some gauges are affected. The code is generic and does not say more precisely what type of fault it is.
Possible causes
- The negative wire of the high speed CAN has contact with supply voltage
What you can do
- 1Note when the faults occur, for example at start, under acceleration or at steady speed
- 2Check the high speed harness for chafing, pinch damage and moisture
- 3Check the network connectors for loose connections and corrosion
- 4With a diagnostic tool, read the fault codes from all control modules and see which ones show communication faults
- 5Use a multimeter to check that the negative wire has no contact with supply voltage when it should not
- 6If the engine stalls while driving, avoid long journeys and have a workshop trace the fault promptly
Symptoms you may notice4
- The engine does not start even though the starter turns
- Poor performance and lack of power
- The throttle response hesitates or is jerky
- The speedometer shows wrong readings
General guidance for car owners. Diagnosis on the car can point to a different cause.