P2279 OBD-II Trouble Code: Intake Air System Leak

P2279 code definition

Intake Air System Leak

What the P2279 code means

P2279 is an OBD-II generic code for the engine control module (ECM) detecting a vacuum leak into the engine. This means that unmetered air is entering the engine without the engine sensing it going through the mass air flow sensor and throttle body.

What causes the P2279 code?

• The engine control module (ECM) calculates the amount of air going into the engine through the positive crankcase ventilation (PCV) system. If the amount of air is more than expected then the Check Engine Light will come on and code P2279 is set.

• The ECM learns the throttle opening angle and stores it in memory. If the throttle body is cleaned or adjusted without the throttle relearn process performed, then the code may be set.

• The PCV valve or hose is leaking or cracked causing excess air to get into the engine unmetered.

What are the symptoms of the P2279 code?

• The Check Engine Light will be illuminated and the code is set in the ECM memory as a fault.

• The engine may run very rough and stall if the vacuum leak is major.

• The engine may run lean and misfire.

• The fuel mileage may be more than before failure since the ECM will try and compensate for the excess air in the engine detected by the O2 sensors.

How does a mechanic diagnose the P2279 code?

• Scans for codes and documents any codes in the ECM, then looks at the freeze frame data for failure

• Listens to the engine for any vacuum leaks, broken, or loose vacuum hoses or air inlet hoses

• Removes the PCV valve and checks to make sure it is not stuck in the open position

• Checks the throttle body to see if it was recently cleaned and allows relearning of the throttle position, then clears the codes and retests

Common mistakes when diagnosing the P2279 code?

• Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so the failure may be duplicated and repaired

• Cleaning the throttle body and not relearning the throttle position again

• Adjusting the throttle plates to compensate for a vacuum leak

How serious is the P2279 code?

Code P2279 is a code indicating that the ECM is detecting that the engine has too much air entering and sees this as a vacuum leak. An engine running with too much air will run lean and cause the engine to run rough and stall at low engine speeds.

What repairs can fix the P2279 code?

• Repairing or replacing the PCV valve or hose
• Replacing leaking intake gaskets or seals
• Relearning the throttle position for the ECM

Additional comments for consideration regarding the P2279 code

Code P2279 can be from any kind of vacuum leak in an engine. Some vehicle manufacturers may use different lean codes instead of this code. The code can be generated from a throttle body or idle air control valve cleaning. This can cause the engine to have to lower the throttle plate to maintain the correct idle speed and see this as excess air entering the engine causing the P2279 code to turn on. A simple relearn of the base idle will fix most of these problems.

Need help with a P2279 code?

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