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P2279: Intake air system leak

The ECU detects air entering the engine without passing the air flow sensor. Usually a split vacuum hose, a gasket or a loose intake hose.

Code P2279 at a glance
CodeP2279
SystemEngine and transmission
GroupP22xx, NOx sensors, oxygen sensors and emissions
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P2279 means

The ECU works out the fuel from the air measured by the air flow sensor. If air gets in somewhere else (a leak after the sensor), the mixture goes lean and the figures no longer add up. This code means it has spotted that leak by comparing several readings, such as manifold pressure and measured air flow.

Most common causes

  • Split, loose or disconnected vacuum hose
  • Loose or split hose between the air flow sensor and throttle
  • Broken crankcase ventilation (PCV) valve or hose
  • Leaking intake manifold or throttle body gasket
  • Leaking brake servo hose
  • Oil filler cap or dipstick not seated properly

Symptoms

  • Engine warning light on
  • Rough or high idle
  • Hissing sound from the engine bay
  • Hesitation and sometimes lean mixture codes

Can you drive with P2279?

With care The car can be driven, but find the leak soon: a lean mixture makes the engine run worse and can lead to misfires.

How to check it

With the engine idling, listen for a hiss and make sure the oil filler cap and dipstick are properly in place. Live data showing strongly positive fuel trims at idle that improve with revs confirms an air leak.

How to read and clear P2279 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P2279 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P2279 is a generic code, so it means the same on any make, for example on BMW, Ford, Mercedes-Benz, Renault, Volkswagen, Volvo. See what Final OBD does on your car in makes and models.

What does code P2279 mean?

The ECU works out the fuel from the air measured by the air flow sensor. If air gets in somewhere else (a leak after the sensor), the mixture goes lean and the figures no longer add up. This code means it has spotted that leak by comparing several readings, such as manifold pressure and measured air flow.

Can you drive with P2279?

The car can be driven, but find the leak soon: a lean mixture makes the engine run worse and can lead to misfires.

How do you clear P2279?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P2279 comes back.