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Home / Codes / P2279
DTC code page

P2279: Intake Air System Leak

Quick answer: The PCM believes unmetered air is entering or the intake system is leaking in a way that disrupts load calculation.

Drivers also search this fault as intake air system leak, unmetered air leak code, P2279 intake leak.

Severity: medium Family: powertrain Related paths: 13
Meaning

What P2279 usually means

P2279 is one of the better generic codes because it points directly at the real-world problem: the engine sees an intake leak serious enough to upset the airflow model. Depending on the platform, that can mean a split intake boot, torn PCV hose, manifold leak, disconnected brake-booster line, loose charge pipe, or any opening that lets air bypass the expected measuring path. It is popular in search because it often creates rough idle, lean trim, whistling noises, and a car that feels slightly off without giving one glamorous part-failure answer.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Start with a visual and hands-on intake inspection because many P2279 cases are literally a hose or boot problem hiding in plain sight.
  • Listen for hissing and compare fuel trims at idle versus cruise because leak behavior often looks much worse at idle.
  • Ask whether the code appeared after air-filter, throttle-body, turbo plumbing, or PCV service.
Driving risk

Can you keep driving?

Many P2279 cases are driveable short-term, but a real intake leak can worsen lean operation, idle quality, and turbo or crankcase-control behavior. Diagnose it before small air leaks turn into bigger secondary problems.

Moderate urgency: This code often allows short-term driving, but the right fix usually comes faster when you diagnose it early instead of waiting for more codes.
Symptoms

Common symptoms

Likely causes

Common causes behind this code

  • Split or loose intake boot, duct, or charge pipe
  • PCV hose or crankcase ventilation leak creating unmetered air
  • Intake manifold, throttle-body, or gasket leak
  • Brake-booster or vacuum accessory hose leak
  • Sensor housing or hose routing disturbed during recent maintenance

Cause phrases often tied to this code: vacuum leak, split intake boot, PCV hose leak, manifold gasket leak, brake booster leak, charge pipe leak.

Diagnostic order

Suggested workflow

  1. Inspect the intake path from air box to manifold for cracks, loose clamps, disconnected vacuum tees, or split PCV plumbing.
  2. Check short-term and long-term fuel trim at idle and at a light cruise to see whether the leak behaves like classic unmetered air.
  3. Smoke test the intake system if the leak is not obvious by sight and sound.
  4. Inspect manifold and throttle-body sealing surfaces if trims stay lean and no hose fault is visible.
  5. Only replace sensors after the air path is proven sealed and the live data still does not make sense.
Avoid guesswork

Common mistakes

  • Replacing the MAF or O2 sensors before checking for a torn intake boot or failed PCV hose.
  • Ignoring a small hissing noise because the vehicle still mostly drives normally.
  • Clearing the code without comparing idle and cruise fuel-trim behavior first.
Repair path

Practical fix guidance

  • Repair the actual intake leak, whether it lives in a duct, gasket, PCV branch, or vacuum accessory line.
  • After repair, confirm trims normalize at idle and the idle quality improves before calling it fixed.
  • If reduced power or correlation codes accompanied P2279, verify they do not return once the intake path is sealed.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P2279

Useful when the driver knows the wording but not the exact DTC yet.

  • intake air system leak
  • unmetered air leak code
  • P2279 intake leak
Related search intent

Queries this page can answer naturally

  • P2279 code meaning
  • what does P2279 mean
  • intake air system leak symptoms
  • P2279 vacuum leak or PCV
FAQ

Quick questions about P2279

Is P2279 basically a vacuum leak code?

Very often, yes. It usually means unmetered air is entering somewhere in the intake system.

Can a bad PCV hose cause P2279?

Absolutely. Cracked or disconnected PCV plumbing is a classic real-world trigger.

Should I replace the MAF for P2279?

Not first. Intake leaks are more common than a magically failed MAF when this code appears.