VOLVO
CEM-1A21 - Increased power supply relay. Signal too high. Intermittent fault
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
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 has registered that the relay driver for the extended X-supply relay is short-circuited to supply voltage, and the fault is intermittent. It was present at an earlier time but is no longer there. The relay may be installed incorrectly or have poor contact.
Possible causes
- Incorrectly installed relay
- Contact resistance in the relay terminals
What you can do
- 1Check that the relay sits correctly in its place and is fully pushed in
- 2Check that the relay connectors are secure and clean
- 3Clear the code and road test the car to see whether it returns
- 4If the fault returns, have a workshop replace the relay
Symptoms you may notice3
- Power seat does not operate at all
- No gauges are working
- The instrument lighting does not operate
General guidance for car owners. Diagnosis on the car can point to a different cause.