VOLVO
CEM-1C05 - 30 Power supply. Signal too low. 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 supply voltage from the battery to the CEM (30-supply) has been too low at some point. The fault is intermittent, so it may not be present right now. The cause is often poor contact in the connections, a weak battery or a defective generator.
Possible causes
- Contact resistance or poor connections
- A weak battery that needs charging, giving low voltage
- A defective generator
What you can do
- 1Check that the battery terminals and connections are clean, tight and free of corrosion
- 2Check that the cables between the battery, generator and starter motor are intact and not chafed. Use a multimeter to check they have no break
- 3Check that the battery is charged. Charge it if needed
- 4Check the generator connections and the connectors to the CEM. With a diagnostic tool, follow the battery voltage in live data with the engine running
- 5After the work, clear the code and check that the charging warning does not light again
Symptoms you may notice4
- The charging lamp lights while the engine is running
- The headlight bulbs burn out
- The starter motor turns slowly
- The battery discharges
General guidance for car owners. Diagnosis on the car can point to a different cause.