VOLVO
CEM-B109719 - Heated Windshield Relay. General Electrical Failures. Circuit current above threshold
System
Central Electronic Module (CEM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsV40 (2013–), V40 Cross Country (2013–)
Show models by year and engine (2)
What does this fault code mean?
The CEM controls the front windscreen defroster through a relay. The fault shows that the relay cannot be activated when the defroster is switched on with the engine running, which suggests the control signal to the relay is shorted to voltage.
Possible causes
- The control wire for the defroster relay is shorted to voltage
What you can do
- 1Read off and note the code, clear it and check whether it returns when you switch the defroster on with the engine running
- 2Check that the fuses for the front windscreen defroster are intact
- 3Check that the connectors in the defroster wiring harness are fully engaged and not damaged
- 4Use a multimeter (ignition off, connector unplugged) to check that the relay control wire is not at battery voltage
- 5If you have a diagnostic tool, activate the front windscreen defroster with the tool and check that it starts
- 6If the fault remains, have a workshop check the relay and the wiring
Symptoms you may notice1
- Windscreen defog and defrost does not work
General guidance for car owners. Diagnosis on the car can point to a different cause.