Intake Air System Leak
The P2279 code means the vehicle's onboard diagnostic system has detected: Intake Air System Leak. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $50 - $400 (parts and labor)
Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
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
Common Fixes by Vehicle
What techs usually find when diagnosing P2279 on specific vehicles — tap your vehicle for the fix and the exact part:
2011-2019 Ford F-150 3.5L/2.7L EcoBoost moderate DIY
Ford EcoBoost P2279 is a MASSIVE search topic -- intake air system leak. The #1 cause is a split charge pipe (plastic intercooler hose) or a torn boot between turbo and throttle body. Pressure-test with a Redline Charge Pipe Tester at ~20psi.
Labor: 2-3 hours2013-2018 Ford Escape/Fusion 1.6L/2.0L EcoBoost hard DIY
Failed intake manifold gasket or warped plastic manifold. EcoBoost manifolds warp over time; replace with updated Ford Performance manifold or a Dorman upgraded unit. Don't skip new gaskets and torque sequence.
Labor: 4-5 hours2012-2018 Ford Focus ST/Fiesta ST 2.0L/1.6L EcoBoost easy DIY
Torn PCV hose, valve cover breather, or CCV diaphragm. Smoke test the entire crankcase ventilation system. Ford issued TSB 14-0194 covering PCV updates. Replace all suspect hoses with Motorcraft originals -- aftermarket rubber fails quickly.
Labor: 1-2 hoursFrequently 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.
Sources
This page is built from documented references. Verify against your own service info before repair work.
See All Codes & Fixes for Your Vehicle
Explore More
Was this helpful?
Share carcodefinder.com with a friend who needs to decode their check engine light.