Intake Air System Leak
The P2279 code indicates that the Powertrain Control Module (PCM) has detected a leak in the intake air system downstream of the mass air flow (MAF) sensor. This allows unmetered air to enter the engine, causing a lean air-fuel mixture. Common causes include cracked or disconnected vacuum hoses, a faulty intake manifold gasket, or a damaged PCV valve. The leak disrupts the calculated air-fuel ratio, leading to performance issues and potential engine damage if left unaddressed.
01. Most Common Causes
- Cracked or disconnected vacuum hoses
- Faulty intake manifold gasket
- Damaged PCV valve or hose
- Loose or missing oil filler cap
- Cracked air intake duct
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or stalling
- Lean air-fuel mixture (P0171 or P0174 may also be present)
- Decreased engine performance and fuel economy
- Hissing sound from engine bay
03. Step-by-Step Diagnosis
Step 1: Visually inspect all vacuum hoses and intake ducts for cracks, disconnections, or damage.
Step 2: Use a smoke machine to pressurize the intake system and locate the leak.
Step 3: Check the PCV valve and hose for proper operation and sealing.
Step 4: Inspect the intake manifold gasket for signs of leakage.
Step 5: Verify the MAF sensor readings and fuel trims using a scan tool.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive for extended periods as the lean condition can cause engine misfires, overheating, and damage to the catalytic converter. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the source of the leak. Simple hose replacements are cheaper, while intake gasket repairs may cost more.