VOLVO
CEM-4F30 - Battery temperature. Signal too high
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
5 modelsC30 (2007–2013), C30 Electric (2011–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
What does this fault code mean?
The CEM calculates the battery temperature from the battery temperature sensor. If the sensor circuit is shorted to supply voltage or has a break, the code is set. The battery may then discharge, and the battery temperature may be shown wrongly.
Possible causes
- Contact resistance in the control module connector
- An open circuit in the signal ground wire
- An open circuit in the signal wire, or the signal wire is shorted to supply voltage
- A damaged battery temperature sensor
What you can do
- 1With a diagnostic tool, follow the battery temperature in live data and check that the value is reasonable
- 2Check that the connectors at the battery and at the CEM are seated and not corroded
- 3Use a multimeter to check that the signal wire from the battery sensor has no break or short to supply voltage
- 4If the fault remains, have a workshop replace the battery temperature sensor
- 5After the work, clear the code and check that the battery charges normally
Symptoms you may notice1
- The battery discharges
What the fault can affect1
- The battery temperature is shown wrongly
General guidance for car owners. Diagnosis on the car can point to a different cause.