VOLVO
CEM-U000188 - High Speed 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:
9 modelsS60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V60 Cross Country (2015–), V70 (2008–), XC60 (2009–), XC70 (2008–)
What does this fault code mean?
The module has disconnected itself from the high speed CAN, so-called bus-off, after its message traffic became faulty. The cause is most often a break in one or both CAN wires in part of the network, or a short between the internal CAN wires. Starting and driving can then be affected.
Possible causes
- Open circuit in one or both CAN wires in part of the network
- Short circuit between the internal CAN wires
What you can do
- 1Clear the fault codes, start the car and read them again. If bus-off returns straight away, the fault is active
- 2Check the high speed harness for breaks, chafing and pinch damage, especially where it passes through a grommet
- 3Check the connectors on the network for loose connections, corrosion and moisture
- 4With a diagnostic tool, read the fault codes from all control modules. A module that has gone into bus-off often shows no other faults
- 5Gently flex the harness with the ignition on and see whether the fault code changes
- 6Have a workshop measure the resistance on the network, since it requires the network to be separated
Symptoms you may notice5
- The engine does not start even though the starter turns
- Poor performance and lack of power
- The throttle response hesitates, surges or is jerky
- Cruise control cannot be engaged
- The speedometer and tachometer show wrong readings
What the fault can affect2
- The module switches itself off (bus-off) and stays off until its power supply is cut
- At the next power-up the module makes new attempts to communicate
General guidance for car owners. Diagnosis on the car can point to a different cause.