VOLVO
EFI-0012 - Volume air flow (VAF) sensor
System
Electronic Fuel Injection (EFI)
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:
2 modelsS40 (1996–2004), V40 (1996–2004)
Show models by year and engine (2)
What does this fault code mean?
The volume air flow sensor measures how much air flows into the engine, and the engine control module uses this value to control fuel injection. The code is set when there is a fault in the sensor or its wiring, and the engine then runs only on a rich mixture of fuel and air.
Possible causes
- Defective volume air flow (VAF) sensor
- Open circuit in the signal cable
- Signal cable short-circuited to ground or supply voltage
- Contact resistance
What you can do
- 1Read the other fault codes in the engine control module. If any of EFI-0012, EFI-0013, EFI-0021, EFI-0025, EFI-0056 or EFI-0066 is also stored, investigate it first.
- 2Check that the connectors to the air flow sensor and the control module are secure and free from contact resistance and oxidation.
- 3With a multimeter, check that the signal wire is not broken and not short-circuited to ground or voltage.
- 4If you have a diagnostic tool, read the air flow value in live data with the engine idling. The value should rise when the accelerator is pressed.
- 5If no fault is found in the wiring, the air flow sensor needs replacing. Have a workshop do this.
Symptoms you may notice1
- The malfunction indicator lamp lights up
What the fault can affect3
- The engine runs only on a rich fuel and air mixture
- Closed-loop control is not active
- Ignition and fuel injection are instead controlled from the throttle position sensor and the flywheel sensor values
General guidance for car owners. Diagnosis on the car can point to a different cause.