P2279: Intake Air System Leak

What it means

The ECU has detected a discrepancy between commanded throttle/intake conditions and the resulting MAP/MAF that points to unmetered air entering after the throttle body. On turbocharged engines this often means a cracked or disconnected boost pipe between turbo and intake; on naturally aspirated engines, a hole in the intake manifold or hose.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The intake air system carries air from the air metering and throttle area into the engine. The control module compares throttle, manifold pressure, and airflow readings; this code sets when those readings suggest air is entering downstream of the throttle without being properly accounted for, such as through a split intake hose or disconnected boost pipe.

Common causes

Most likely first.

1. Boost pipe disconnected or cracked
2. Intake hose split

Symptoms

• Check-engine light on
• Rough or unstable idle
• Hissing or whistling from the intake
• Hesitation or reduced power
• Increased fuel consumption

How to diagnose it

1. Read freeze-frame data and compare live MAF, MAP, throttle position, and fuel trims at idle and under light acceleration to see when the airflow discrepancy appears.
2. Inspect the intake hose, manifold connections, clamps, and any turbo boost pipes for splits, loose joints, or disconnected sections.
3. Listen for hissing or whistling around the intake while the engine idles, taking care to keep clear of moving parts.
4. Check vacuum lines and intake fittings for leaks, then use an appropriate smoke test if a visual inspection does not locate the leak.
5. Recheck the system under the conditions in the freeze frame and confirm fuel trims and airflow readings return toward normal after repairs.

Common fixes

• Reconnect a detached intake or boost pipe and secure its clamps.
• Replace a split intake hose or cracked boost pipe.
• Repair a leaking manifold connection or vacuum line.
• Replace a damaged intake fitting or seal identified by leak testing.

Can I keep driving?

A mild leak may allow a short drive, but avoid hard acceleration and boost because a larger leak can cause power loss, unstable running, or engine management problems. Stop if the engine stalls, runs very roughly, or loses substantial power.