VOLVO
DEM-U000188 - High Speed CAN Communication Bus. Bus Signal / Message Failures. Bus off
System
Differential Electronic Module (DEM)
Volvo models this fault code applies to
Applies to the following models:
8 modelsS60 (2011–), S80 (2007–), V40 Cross Country (2013–), V60 (2011–), V60 Cross Country (2015–), V70 (2008–), XC60 (2009–), XC70 (2008–)
What does this fault code mean?
The four-wheel drive control module (DEM) has switched off its communication on the CAN network, a state known as bus off. It happens when another control module on the network disturbs communication, or when the DEM's own messages cause disturbance. The module then loses contact with the network, and four-wheel drive works with reduced function.
Possible causes
- Short circuit between the CAN wires
- Open circuit in one of the CAN wires
- Internal fault in another control module on the same part of the CAN network
- Internal fault in the control module
What you can do
- 1Read off the fault codes, note them and clear them. Test drive the vehicle to see if the fault returns
- 2Check that the fuses are intact and that the battery is in good condition
- 3Follow the CAN wiring between the control modules for chafing, pinched areas and loose connectors, and check that the connectors are firmly seated and free from oxidation
- 4If you have a diagnostic tool, check which control modules respond on the CAN network and note whether any are missing
- 5If the fault keeps returning, have a workshop measure the CAN network and locate the control module that is disturbing communication
Symptoms you may notice1
- Four-wheel drive does not work
What the fault can affect2
- Four-wheel drive works with reduced function
- The control module switches itself off and stays off until the power supply to it has been broken
General guidance for car owners. Diagnosis on the car can point to a different cause.