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 |
|---|---|
| System | Engine and transmission |
| Group | P22xx, NOx sensors, oxygen sensors and emissions |
| Type | Generic: 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.
Open the bonnetthe in-depth explanation
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 its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
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 an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P2275 The signal from heated lambda sensor 3 on bank 1 stays at rich mixture
- P2276 The signal from heated lambda sensor 3 on bank 2 stays at lean mixture
- P2277 The signal from heated lambda sensor 3 on bank 2 stays at rich mixture
- P2278 The signals from heated lambda sensors 3 on banks 1 and 2 are swapped
- P227A The barometric pressure sensor C has an electrical fault
- P227B The barometric pressure sensor C gives readings outside the normal range
- P227C The barometric pressure sensor C gives a lower signal than normal
- P227D The barometric pressure sensor C gives a higher signal than normal
- P2200 NOx sensor circuit fault (bank 1)
- P2201 NOx sensor circuit range or performance problem (bank 1)
- P2227 Barometric pressure sensor A range or performance problem
- P2228 Barometric pressure sensor A circuit low
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.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
