VOLVO
EFI-0066 - Brake vacuum sensor. Faulty signal
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 signal from the brake vacuum sensor to the engine control module is faulty. The fault can lie in the sensor or in the wiring and connectors to it. The fault code lights the malfunction indicator lamp and makes the engine run only on a rich fuel/air mixture.
Possible causes
- Contact resistance at the connectors
- Short circuit to ground or supply voltage in the signal wire
- Open circuit in the signal wire
- The brake vacuum sensor is defective
What you can do
- 1Read other fault codes and write them down before you replace any part
- 2Use a multimeter to check that the wiring to the brake vacuum sensor has no break and is not shorted to earth
- 3Check the connectors at the sensor and the control module
- 4If you have diagnostic equipment: read the brake vacuum sensor value in live data and check that it changes when the brake pedal is pressed with the ignition on
- 5If the wiring is intact, replace the brake vacuum sensor and check that the fault code does not return
Symptoms you may notice1
- Malfunction indicator lamp (MIL) comes on
What the fault can affect1
- The engine runs only on a rich fuel/air mixture
General guidance for car owners. Diagnosis on the car can point to a different cause.