VOLVO
CEM-U300049 - Control Module. System Internal Failures. Internal electronic failure
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 CEM checks its outputs for short circuits that could harm the module. The fault is stored when an output has been short-circuited so many times, or with short circuits that were never fixed, that its service life is used up. The output is then permanently disabled, and clearing the code does not help.
Possible causes
- Internal fault in the CEM due to unrectified or recurring short circuits on the same output
What you can do
- 1If you have a diagnostic tool, read the codes in the CEM and note any other codes relating to short circuits on outputs
- 2Fix the cause of the short circuit first: look for chafing, pinch damage and damaged connectors on the wiring to the function that does not work
- 3Use a multimeter to check that the wiring has no contact with earth (the body) or voltage where it should not be
- 4Safety: if the airbag warning lamp is involved, have a workshop check the airbag system; do not work on it yourself
- 5Once the cause is fixed, have a workshop replace the central electronic module (CEM), since the output cannot be restored
Symptoms you may notice5
- The engine does not crank or does not start
- Tail light or brake light does not work
- Front or rear turn signals do not work
- Cabin heating is absent or slow to warm up
- The supplemental restraint system (SRS) warning lamp comes on or behaves abnormally
What the fault can affect1
- The output causing the fault is permanently disabled and cannot be activated again
General guidance for car owners. Diagnosis on the car can point to a different cause.