VOLVO
CEM-1A01 - Upper 30-power supply Open circuit
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
What does this fault code mean?
The CEM is supplied from the battery through two separate inputs. If the upper 30 supply is open, the module has no voltage on that side, so for example only one side of the exterior lighting may lack power. The fault is caused by an open circuit or a short to ground in the supply, or by a blown fuse.
Possible causes
- Open circuit or short to ground on the upper 30 supply
- Blown fuse in the battery main fuse box
What you can do
- 1Check whether the main fuse at the battery has blown and replace it if needed
- 2Check with a multimeter that the wire between the CEM and the main fuse is not open when the connectors are disconnected
- 3Check with a multimeter that the wire has no contact with ground (the bodywork) when the connectors are disconnected
- 4Check that the connectors are secure and free from corrosion and looseness
- 5If the fault remains, have a workshop continue the fault-tracing
Symptoms you may notice5
- The engine does not start
- The headlights do not work
- The tail lights or brake lights do not work
- The turn signals do not work
- The windscreen washers do not work
General guidance for car owners. Diagnosis on the car can point to a different cause.