Intake Air System Leak
What does P2279 mean?
The P2279 code means the vehicle's onboard diagnostic system has detected: Intake Air System Leak. This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Rough or unstable idle
- Hissing or whistling sound from engine bay
- Lean fuel trim readings
- Hesitation on acceleration
Probable Causes (Ranked by Likelihood)
- Cracked or disconnected intake hose or boot Very High
- Leaking intake manifold gasket High
- Broken PCV valve or hose allowing unmetered air Moderate
- Loose or cracked vacuum line Moderate
- Faulty brake booster check valve leaking air Low
Step-by-Step Diagnostic Procedure
-
Perform a smoke test on the intake system to locate the leak
-
Visually inspect all intake hoses, boots, and clamps for cracks or loose connections
-
Check the intake manifold gasket area for signs of leak
-
Inspect PCV system hoses and valve
-
Listen for hissing sounds while the engine is idling
Frequently Asked Questions
What is an intake air system leak?
An intake air system leak means unmetered air is entering the engine after the mass airflow sensor. This extra air is not accounted for in the fuel calculations, causing a lean condition.
How do I find the leak?
The most reliable method is a smoke test, where a smoke machine pressurizes the intake system so you can see where smoke escapes. You can also listen for hissing sounds or spray soapy water on suspected areas.
Can a small leak cause big problems?
Yes, even a small leak can cause rough idle, poor fuel economy, and lean misfire codes. The engine relies on precise air measurement for proper fuel delivery.