P2279 means Intake Air System Leak. The computer has detected air entering the engine without being measured, usually through a leak in the intake, and the fuel mixture has gone lean. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P2279 means
The engine computer keeps adjusting fuel to hold the air-fuel mixture near the ideal ratio, using oxygen sensor feedback. Those adjustments are fuel trims: short-term trim reacts instantly and long-term trim learns over time. Positive numbers mean the computer is adding fuel; negative numbers mean it is taking fuel away. When long-term trim sits near the limit the computer allows, it sets a lean or rich code. On a V engine, bank 1 is the side containing cylinder 1 and bank 2 is the opposite side; inline engines only have bank 1.
P2279 symptoms
- Check engine light
- Rough or high idle
- Hissing noise from the engine bay
- Lean codes P0171 or P0174
Common causes of P2279
- Cracked or loose intake duct after the MAF sensor
- Leaking intake manifold gasket
- Split vacuum or PCV hose
- Leaking brake booster hose
- Throttle body gasket leak
How to diagnose P2279
- Inspect the intake ducting and clamps
- Smoke test the intake for leaks
- Check fuel trims at idle and at higher rpm
- Check the PCV system
Can you drive with P2279?
Usually yes in the short term, but a lean engine can misfire; fix the leak.
P2279 tips
A smoke test finds intake leaks quickly; split ducts after the MAF sensor are a common cause.
Will P2279 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P2279 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0171 | System Too Lean (Bank 1) |
| P0174 | System Too Lean (Bank 2) |
| P0101 | Mass or Volume Air Flow Circuit Range/Performance |
Guides that help
When it is more than a sensor
Fuel trim codes are almost always fixed with a leak repair, a sensor or a fuel delivery part. If a long-running lean condition has burned a valve or piston and a compression test confirms it, compare repair against a replacement on our engines page and see engine replacement cost.
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