VOLVO
CEM-1C0A - Alternator control module (ACM). Voltage too high
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–)
Show models by year and engine (16)
- Volvo S60 (2001–2009)2005All engines except: B5244S6
- Volvo S60 (2001–2009)2006All engines except: B5244S6, D5244T4, D5244T5, D5244T6, D5244T7
- Volvo S60 (2001–2009)2007–2009All engines except: D5244T4, D5244T5, D5244T7
- Volvo S80 (1999–2006)2005–2006
- Volvo V70 (2000–2008)2005All engines except: D5244T3
- Volvo V70 (2000–2008)2006All engines except: D5244T4, D5244T5, D5244T6, D5244T7
- Volvo V70 (2000–2008)2007All engines except: D5244T4, D5244T5, D5244T7
- Volvo V70 (2000–2008)2008All engines except: D5244T5, D5244T7
- Volvo V70 XC / XC70 (2001–2007)2005
- Volvo V70 XC / XC70 (2001–2007)2006All engines except: D5244T4
- Volvo V70 XC / XC70 (2001–2007)2007Engine B5254T2 only
- Volvo XC90 (2003–)2005All engines except: B8444S
- Volvo XC90 (2003–)2006All engines except: B8444S, D5244T4
- Volvo XC90 (2003–)2007–2012Engine B5254T2 only
- Volvo XC90 (2003–)2013–2014Engine B5254T9 only
- Volvo XC90 (2003–)2015
What does this fault code mean?
The CEM checks the charging status of the battery. The battery voltage is measured by the rear electronic module (REM) and sent to the CEM over the CAN network, so faulty data from the REM can trigger this code. It may also be caused by a damaged charge regulator in the generator control module.
Possible causes
- A battery charger with too high charging voltage was connected earlier
- A damaged generator control module (charge regulator)
What you can do
- 1Check that the battery terminals and cable connections are clean and tight
- 2Use a multimeter to measure the battery voltage with the engine off and running. Large differences point to a charging fault
- 3Check that the connectors to the REM are seated and free of corrosion
- 4If you have a diagnostic tool, compare the battery voltage in live data with the voltage the REM reports. The values should match
- 5After the work, clear the code and check that the charging voltage is normal
Symptoms you may notice3
- The battery electrolyte boils with the engine running
- The headlight bulb burns out
- The engine starts unreliably or not at all
General guidance for car owners. Diagnosis on the car can point to a different cause.