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P2279 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P2279 is an OBD-II Code that refers to Intake Air System Leak


A P2279 code is a generic diagnostic trouble code that occurs when the PCM/ECM detects a signal voltage input indicating a vacuum leak into the engine. Unmetered air is entering the engine without being detected by the mass airflow sensor and throttle body.

If the mass airflow, intake air temperature, and oxygen sensor indicate a discrepancy, the code P2279 is created.


Common causes for this code include:

  • On the engine side, there’s a leak in the air duct
  • There is a gap between the engine side of the mass airflow sensor and the air duct
  • Vacuum hose with a leaky brake booster
  • Intake air temperature sensor has a leak
  • Throttle body is leaking
  • The oil filler cap with a stuck crankshaft
  • Vacuum hose was disconnected or damaged.
  • Intake manifold crack or leak 
  • Faulty fuel injector seal at manifold 
  • Leak under dash at a vacuum operated device 
  • Stuck PCV valve


The symptoms of a P2279 code are:

  • Illuminated Check Engine Light 
  • If there is a significant leak in the vacuum, the car engine may start running erratically or may stall.
  • A lean condition might be prevalent
  • Engine problems linked to misfire
  • Fuel efficiency is altered


To diagnose a P2279 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the air duct for any leaks.
  3. Check the gap between the mass airflow sensor and air duct.
  4. Inspect the vacuum hoses for any leaks.
  5. Check the intake air temperature sensor for any leaks.
  6. Inspect the throttle body for any leaks.
  7. Check under the dash at a vacuum operated device for any leaks. 
  8. Check the PCV valve.
  9. Check the intake manifold for any cracks or leaks. 
  10. Check the fuel injector seal at the manifold.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P2279 code:

  • Not thoroughly inspecting all the wiring and connectors.
  • Not checking the entire air intake system for leaks.
  • Not checking the throttle body for vacuum leaks.
  • Failing to check the intake air temperature sensor for a vacuum leak.

How serious is this?

A P2279 code is considered a serious fault and should be addressed as soon as possible. If the code is not fixed, it may lead to further engine damage, especially if neglected for an extended period of time.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Repair or replace any faulty parts such as wiring, connectors, or hoses.
  • Clean or replace the mass airflow sensor.
  • Check and replace the vacuum hoses.
  • Replace the intake air temperature sensor.
  • Repair or replace the throttle body.
  • Check for leaks and seal any that are found.
  • Replace the PCV valve.
  • Repair or replace the intake manifold.
  • Replace the fuel injector seal at the manifold.

Related codes

A P2279 is related to and may be accompanied by the following codes:

P0455 – EVAP System Large Leak

P0499 – EVAP System Vent Control Circuit High

P0171 – Lean Exhaust Condition

P0174 – Lean Exhaust Condition


In conclusion, the P2279 code is a diagnostic trouble code that refers to a problem with the intake air system. The code may be caused by a number of factors, such as a leak in the vacuum hoses, an intake manifold crack or leak, or a faulty fuel injector seal at the manifold. The code should be addressed as soon as possible to prevent further engine damage.