P2279 Diagnostic Trouble Code: An In-depth Analysis

The illumination of the check engine light indicates something is wrong with the engine. However, it cannot show what exactly is happening under the hood. That’s why, you’ll need to diagnose the engine with a scan tool to pull out a registered fault for what’s wrong.

If the diagnostic machine pulls error code P2279 on Peugeot or your respective car model, it means there’s an intake air leak somewhere in the system. This article will discuss the symptoms, causes, diagnostic mistakes, and how to diagnose and rectify the root cause of error code P2279 diagnostic trouble code. But first, let’s see the meaning of this fault code.

p2279 intake air system leak detected

What does error code P2279 mean?

When the car computer logs error code P2279, the powertrain control module (PCM) has detected a leak in the intake system. The PCM/ECM detects this air leak through the readings from the mass air flow sensor, oxygen sensor, and/or air intake temperature sensor.

These car sensors measure the amount of oxygen entering or going out of the engine. These sensors report their readings to the engine control module through a voltage signal.

For instance, the downstream oxygen sensor should send 450 millivolts to the car computer per second. If it sends 10 millivolts per second, it means there’s too much oxygen in the exhaust gas. Too much air could emanate from air leaks in the intake lines.

The powertrain control module detects leaks through readings from the air intake temperature sensor, oxygen sensor, and/or mass air flow sensor. By default, the PCM has a predefined air ratio it should detect in the system. If the current readings fall outside the predefined ratio, it will log diagnostic trouble code P2279 on VW GTI or your respective car model.

The car computer needs the predefined air ratio to determine and fine-tune the engine operations in every given situation. The ECM needs to adjust the air-fuel ratio and the timing in certain environments to suit the needed power.

If unmeasured air enters the system, the PCM will make wrong estimates in adjusting the system operations. Alarming is, this will affect the overall system operations.

What are the symptoms of error code P2279?

Like other too much air or air leaks related error codes, the P2279 on VW Jetta or any car model will leak a few symptoms to notify the driver of an underlying issue that needs attention. Here are the symptoms you should watch out for.

Check engine light

The engine warning light is the most prevalent sign of a P2279 trouble code across all car models. The check engine light appears on the dashboard whenever the engine malfunctions or when the powertrain control module detects any issues with any car sensor or system component.

However, it does not point out a specific problem. Instead, this means several issues can cause the car computer to project the engine warning light on the dashboard. Therefore, it is important to diagnose your car whenever the check engine light appears on the dashboard to figure out what’s happening under the hood.

Poor engine performance

Since the engine control module works with the received data, it’ll make a wrong estimate once there’s unmeasured air in the system. This wrong estimate will lead to rough idling, engine stalling, poor acceleration, and loss of engine power while driving.

High gas consumption

By default, the engine control module will send more fuel to the combustion chamber to compensate for the air-to-fuel ratio once it senses more air in the system. Whether you have a P2279 on Vauxhall or a P2279 on Audi Q7, the car computer will send more fuel to the combustion chamber. This extra fuel means constant visits to the gas stations and extra bucks on fuel.

What Causes error code P2279?

As reiterated above, a P2279 fault code means the ECM has detected air leaks in the system. The air can be coming from anywhere in the system. When diagnosing, you need to track where the air leak is coming from to know how to proffer solutions.

In the case of a P2279 on a Mercedes or your respective car model, the air is not leaking from the air filter or before the mass air flow sensor because the ECM does not monitor these places. The leaking is happening after the MAF sensor, anywhere around the intake manifold, the throttle body, to the exhaust system. Here are the possible causes you should look into.

Malfunctioning intake air temperature

If there’s a leak in the IAT sensor seal, the IAT sensor, O2 sensor, and the mass air flow will signal the PCM via a voltage reading. In return, the PCM will log a P2279 to help the car owner or service technician know what’s going wrong with the system.

If the IAT sensor malfunctions, it can also send false readings to the car computer, saying there’s too much air in the system even when everything is running fine.

Disconnected vacuum hose

If the vacuum hose is disconnected or broken, it’ll introduce unmeasured air into the system. This will cause the engine control unit to log error code P2279 on Honda or your respective car model.

Broken positive crankcase ventilation (PCV hose)

The engine control unit measures the amount of air entering the engine through the PCV hose. If it detects unmeasured air, it’ll log a P2279 on its memory for the car owner or service technician to easily detect what’s wrong.

Throttle body leaks or other issues

The car computer learns your driving style, the throttle body opening angle, and stores the data in its memory. If you adjust or clean the throttle body without performing a relearning process, the PCM may throw a P2279 code.

There are other possible causes you should look into. These includes

  • Leaking fuel injector seal
  • A leak in the engine-side air duct
  • Leaking brake booster vacuum hose
  • Purge line leak
  • PCV hose leak
  • Incorrect camshaft timing
  • Throttle body leaks or throttle body seal leaks
  • Manifold gasket seal leaks
  • Manifold leaks.

How serious is error code P2279?

As reiterated above, the P2279 error code shows the powertrain control module has detected air leaks or too much in the system. And it sees this as a vacuum leak. If eventually, there’s an introduction of unmeasured air in the system, it’ll cause the engine to run lean. This will affect the overall engine perfection and invariably cause a soft engine seize.

A soft engine seize is a damage caused by friction between the cylinder walls and the pistons. It happens due to a momentary dry spot in the engine where the metal surfaces come in contact. This contact causes friction damage or burns. However, a P2279 is a moderate case because it can lead to a soft engine seizure, but there’s a slim chance to this.

p2279 peugeot

How to diagnose

If you love fixing things at home, you should roll your sleeves and track and rectify the root cause of error code P2279 on VW 1.6 TDI or your respective car model. However, to track and resolve the leading cause of a P2279 error code, you’ll need directives on how to do that.

Items and Tools Needed

  • Diagnostic trouble code scanner
  • Digital Multimeter

Step 1: Scan the vehicle

Locate the vehicle’s diagnostic scanning port underneath the steering wheel and connect the scan tool. After that, read the logged error codes and document them. If the system registers other trouble codes like P0171, P0174, P0300, P2270, or P2271, fix them before proceeding to the next step. 

Step 2: Check vacuum leaks

Since the car computer says there’s an introduction of unmeasured air, you need to track where the air is leaking from and fix it immediately. Start by listening to hissing sounds from the engine bay and narrow it down by checking the intake lines, intake manifold, PCV hose, PCV lines, purge lines, broken or disconnected vacuum hose, and IAT seal leaks.

You can also check the IAT, MAF, and O2 sensors to ensure they are functioning properly and sending the right message to the ECM.

Step 3: Examine the PCV and the throttle body

Inspect the positive crankcase ventilation valve and ensure it is not stuck in the open position. Head down to the throttle body and inspect it. Check if it has been cleaned recently and let the PCM relearn the throttle body. After that, clear the registered fault codes and rescan the vehicle to see if that fixes the underlying P2279 error code.

Step 4: Contact your mechanic

Contact your mechanic for a thorough inspection if none of the above steps could rectify the problem. The mechanic should be able to track the leading cause and proffer solutions to it.

Common P2279 diagnosis mistakes

  • One of the most common diagnostic mistakes amongst DIYers and service technicians is clearing the PCM memory before viewing the freeze frame data. 
  • Cleaning or adjusting the throttle body without relearning the ECM for optimal performance.
  • Adjusting the throttle body plates to compensate for the unmeasured air.

How do you fix P2279?

The following are the necessary repairs to fix P2279 on Ford 1.5 TDCI or any car model. Kindly, note that you need one or more of the following to rectify the P2279 error code.

  • Replacing or repairing PCV valve or hose
  • Relearning the throttle position sensor after cleaning it
  • Tracking and fixing any vacuum leaks in the system.

Approx. Repair Cost

Since air leaks can happen from several areas, it is impossible to say the repair cost without tracking the leading cause. If you want an experienced auto mechanic to track and fix the root cause, he’ll start with an hour of diagnosis.

Most auto mechanics charge $70 to $150 per hour. After the diagnosis, they should be able to pinpoint the cause and estimate the repair cost. We have listed the necessary repairs and amounts to fix DTC P2279 on Volkswagen or your respective car models.

  • Replacing intake manifold gasket $330 to $600
  • Replacing a faulty positive crankcase valve (PCV) $50 to $90
  • Tracking and fixing vacuum air leaks $100 to $500.

Frequently Asked Questions – FAQs

How do you fix a leaking intake air system?

The first thing you need to do is to track where exactly the leaking is coming from. Is it from the manifold or other intake lines? The easiest way to identify where the leak is coming from is by using a smoke tester. To do this, get a smoke testing machine, disconnect the vacuum hose on the brake booster and connect the smoke machine.

Turn on the smoke machine and look for where the smoke is coming out from. Wherever the smoke is coming out from is leaking. Next, determine if you have to replace the component or add some sealant to prevent the leak.

What causes intake air leaks?

The most prevalent cause of intake air leaks is a broken or cracked intake hose or one of the hoses connected to the intake manifold. A bad intake manifold gasket is another common cause to look into. These rubber materials do not last the lifespan of the car. They deteriorate over time and become brittle. As explained above, an intake air leak is easy to find and inexpensive to fix.

Can a leaking intake cause a misfire?

Of course. A leaking intake means there’s an introduction of unmeasured air into the system. This will throw off the calculated air-to-fuel ratio, leading to several engine performance issues like rough idling, loss of engine power while driving, poor acceleration, engine misfire, stalling, stuttering, and even bad gas mileage.

Can I drive with a leaking intake gasket?

This depends on the severity of the leak. A severe intake leak will throw the check engine light and cause performance issues like lack of power, poor acceleration, engine stalling, stuttering, misfiring, and high gas consumption. But if the intake leak is small, it’ll slightly affect the engine performance. You can even drive with it for the next few months.

Can you run an engine without air intake?

Technically, it is not advisable to drive without intake air filters. The sole purpose of the air filter is to filtrate the air that goes into your engine to prevent dirt, debris, and other contaminants from entering the engine.

However, you can drive without the air filter, but this will allow junk and other contaminants to enter the combustion chamber. Therefore, it is better to take precautionary measures unless there’s no alternative to drive without it for a short period.

Final Words

A P2279; intake air system leak detected is a minor to moderate case, which means too much air is making its way into the intake system. In most situations, it won’t prevent you from driving unless in a severe case.

Meanwhile, you need to fix it as soon as you notice reduced engine performance and the check engine light appears on the dashboard. This is because you won’t know when the powertrain control module detects a severe case and project the warning light to notify of the newest issue.

The newest update could be something that needed urgent attention. Ignoring it may cause catastrophic damage to the engine. This is why we have guided you through the process how to track and rectify the P2279 error code to clear the warning light on the dash. Stay alert for new updates.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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