Air intakeGeneric OBD-II codeUrgency: Garage soon
Code P2279: air leak in the intake system
What code P2279 means
The control unit has detected an air leak in the intake system: more air is entering the engine than the sensors measure (unmetered air or "false air"). The mixture becomes lean and the engine loses the regulation it has calculated.[2][4]
On a turbo engine the leak may also be in the boost air circuit. Mitchell 1 documents a P2279 on an Audi A3 1.6 diesel caused by a cracked intercooler, which could not be seen with the naked eye and was found with a smoke test.[1][4]
It is a generic OBD-II code (it starts with P2, and in the P category the second digit 2 also indicates a generic code), so it means the same on any make; what changes from one engine to another is the most likely cause.[5]
Original definition (SAE J2012): Intake Air System Leak[1][2][3]
Causes of P2279
From most to least likely, according to the sources.
- 1Vacuum leaks: cracked, split or disconnected hoses, for example those of the brake servo, the vacuum pump or the throttle body.[2][3][4]
- 2Crankcase ventilation (PCV): stuck valve, torn oil separator diaphragm or faulty system heater (the N79 on some VAG cars).[2][3][4]
- 3Boost air circuit on turbo engines: hoses, connecting pipes or intercooler with micro-cracks that only open under pressure.[1][4]
- 4Intake manifold flaps (swirl flaps) with play in the shafts or with the position out of specification.[3][4]
- 5Manifold and throttle body: cracked manifold, or a manifold or throttle body gasket in poor condition.[2]
- 6Burnt or porous EGR valve flange gaskets.[4]
- 7Leak between the MAF sensor and the air duct, or at the intake temperature sensor.[2]
- 8Injector seals in poor condition.[2]
- 9Faulty mass air flow (MAF) sensor, although a German workshop warns that replacing it without checking the tightness of the intake only treats the symptom.[2][4]
Symptoms
- Engine warning light on in the instrument cluster.[2][3]Engine warning light: faults that cause it
- Uneven idle.[4]Vibrations: faults that cause it
- Whistling or hissing when accelerating.[2][4]Turbo whistle: faults that cause it
- Loss of power under load.[4]Less power: faults that cause it
- Higher fuel consumption.[2]Uses more fuel: faults that cause it
- The engine may stall.[2]Engine stalls: faults that cause it
- Misfires and uneven combustion (knock), due to the lean mixture.[2]
How to diagnose P2279
In order: from the most likely and cheapest to check to the most expensive.
- 1Read the codes and look at the long-term fuel trims (LTFT) at idle and under load: very high values give away extra air.[4]
- 2On Volkswagen 2.5 engines from 2005 to 2013, a manufacturer technical bulletin says to first check the cam timing with the engine idling (the value should be 0 ± 5°) and, if it is correct, continue with the normal diagnosis.[6]
- 3Listen for hissing and visually check hoses, clamps, air ducts, manifold gaskets and intercooler pipes.[2][4]
- 4Carry out a smoke test on the intake and, on a turbo, also on the boost circuit: it finds leaks that visual inspection does not see, such as the cracked intercooler on the Audi A3 documented by Mitchell 1.[1][2][4]
- 5Compare the requested boost pressure with the actual pressure after a burst of throttle: a delay in the pressure rising or a pressure lower than requested points to a leak in the air circuit.[4]
- 6Check the vacuum system (brake servo, vacuum pump, throttle body) before removing anything: it is a cause that is often underestimated.[4]
- 7Check the crankcase ventilation and the manifold flaps. On the VW 2.0 turbo engine (BPY), Ross-Tech notes that a faulty crankcase breather shows up as strong vacuum when you remove the oil filler cap with the engine idling.[3][4]
- 8Do not replace the MAF sensor without having found the leak: according to a German workshop, a dirty MAF sensor gives code P0101, not a leak, and replacing it without checking the tightness only treats the symptom.[4]
Can I keep driving with P2279?
Garage soon
The two sources that assess severity advise against continuing to drive and ask for quick action. Mechanic Base classes it as serious and warns that, with the lean mixture, the engine can suffer permanent damage; a German workshop explains that a lean mixture raises exhaust temperature and, in the long run, damages the exhaust valves, the turbo and the catalytic converter, and can end up generating a P0420.[2][4]
Documented faults related to P2279
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Turbo: the most serious faults by engine and car
- High severityFrequency: Very frequent1.6 HDiTurbo failure through lack of lubrication (carbon deposits and union filter)On the 16-valve 1.6 HDi/TDCi engines (2004-2011) the turbo can seize because carbon deposits from the oil clog the mesh filter in the union that feeds it. It is a serious, repeat fault: if only the turbo is replaced without cleaning the circuit, it fails again.Repair (garage): €700–€1,050
- High severityFrequency: Very frequent2.0 Ingenium diéselTurbocharger failureYes: according to several sources, the turbo is the component that causes the most faults on the 2.0 Ingenium diesel. It fails across a very wide mileage range (from around 35,000 to over 140,000 km) and, if it breaks up inside, it can send oil or metal into the engine and destroy it.Repair (garage): €2,600–€3,000Appears at around 35,000 km
- High severityFrequency: CommonBMW N47Turbo and wastegate valve failureThe N47's turbo does not usually fail from general wear, but because of failure of the wastegate valve, which regulates boost and can seize or lose adjustment, sending fuel consumption soaring; oil leaks from the turbo itself are also common.Repair (garage): €900–€1,800
- High severityFrequency: CommonOM651Variable-geometry turbo failure and its pneumatic actuatorThe OM651's variable-geometry turbo tends to fail at the pneumatic actuator (cracks, loss of calibration) before the turbo itself. Symptoms range from a gradual loss of power to permanent limp mode, with whistling or smoke if the problem progresses.Repair (garage): €500–€3,000
EGR valve: the most serious faults by engine and car
- Critical severityFrequency: Very frequentBMW B47EGR cooler leaks with risk of engine fireYes: the EGR valve cooler can suffer internal coolant leaks which, mixed with soot and oil, can reach combustion temperatures; BMW has launched several technical campaigns since 2018 to inspect and replace it because of the risk of engine fire.Repair (garage): €500–€1,500
- Critical severityFrequency: Very frequentBMW N57EGR cooler leaks with risk of engine fireYes: like the N47 and B47, the N57 is covered by BMW's service campaign for EGR cooler leaks, which can mix coolant with soot and oil to combustion temperatures. BMW checks free of charge the 6-cylinder engines built between July 2012 and June 2015 because of the fire risk.
- High severityFrequency: Very frequentOM651EGR and particulate filter clogging, and emissions software updatesThe particulate filter and EGR clog up with short journeys, as on any diesel with these systems. In addition, Germany's KBA required software updates on several models with this engine between 2018 and 2021 because of a function that reduced EGR outside a temperature range.Repair (garage): €800–€2,500
- Medium severityFrequency: Very frequentOM642Emissions defeat device (AdBlue/EGR) and software update campaignGermany's KBA found indications of emissions manipulation in cars with the OM642 engine (alongside the OM651): AdBlue dosing and the EGR changed between the test bench and the road. Mercedes-Benz denied it, but in 2018 it recalled hundreds of thousands of diesels in Europe.
Intake flaps (swirl flaps): the most serious faults by engine and car
- Critical severityFrequency: Very frequentBMW M47Intake swirl flap breakage (swirl flaps)Yes: the common rail versions of the M47 (built since 2001) have flaps in the intake manifold that, with diesel soot and heat cycles, can break and be sucked into the cylinder, with a risk of serious damage to the piston, cylinder head and valves.
- Critical severityFrequency: CommonBMW N47Broken intake manifold swirl flapsYes: the N47's intake manifold has plastic swirl flaps that, with diesel soot and the passing years, can crack, come loose and be sucked into the cylinder, with a risk of seriously damaging the piston, cylinder head and valves.
- Critical severityFrequency: CommonBMW M57Broken intake swirl flapsYes: most automatic M57 and M57TU engines (330d, 530d, 535d, 730d, X3 3.0d and so on) have six metal flaps in the intake manifold that can seize, come loose and wreck a cylinder. The E53 X5 3.0d and the manual gearboxes of the first 330d/530d are free of them, according to a specialist workshop.
- Critical severityFrequency: CommonOM642Broken swirl flaps in the intake manifoldYes: the plastic rods of the intake manifold's swirl flaps become brittle and can break at around 100,000-200,000 km. If a loose flap is sucked into a cylinder, it can hit the piston and destroy the engine; this is why removing them preventively is recommended.Repair (garage): €600–€1,200Appears at around 100,000 km
Brake servo and vacuum pump: the most serious faults by engine and car
- Critical severityFrequency: Very frequent1.2 PureTechLoss of braking assistance from vacuum pump damageOn 1.2 PureTech turbos built between 2013 and 2018, belt debris can damage the vacuum pump that feeds the brake servo and reduce braking assistance. There were two free recalls (2020 and 2022); it is worth confirming they were done.
- Critical severityFrequency: Occasional1.8 HybridBrake actuator failure (hard pedal, loss of assistance)Yes, it is a documented fault on the Prius III: the diaphragm of the brake actuator's accumulator can degrade and make the pedal very hard, forcing you to brake with much more force. Toyota ran a campaign in 2013; there are also owner reports of actuators failing after the warranty had expired.
- Critical severityFrequency: Very frequentKia Sportage IVBlocked tandem pump filter and loss of brake assistanceYes: a KBA campaign from October 2023 states that the tandem pump filter on Sportages built between 2018 and 2020 has a design defect that can make the brake servo fail and stiffen the brake pedal.
- Critical severityFrequency: OccasionalAlfa Romeo MiToBrake servo pipe connector fault in MiTos built in 2012A 2012 campaign affected MiTos built between 1 June and 30 September 2012: a connector on the brake servo pipe could fail and leave the brakes without vacuum assistance. The record consulted is from the United Kingdom (268 cars); we do not know how many units it affected in Spain.
P2279 by make
Documented faults that can trigger P2279 in each make's engines and cars.
Frequently asked questions
Can I drive with code P2279?
The sources advise against it: the lean mixture heats the exhaust and can damage the valves, the turbo and the catalytic converter, so it needs repairing as soon as possible. If you have to move the car, do so gently and only as far as the workshop.[2][4]
How do you locate the air leak that causes P2279?
With a smoke test, which finds leaks that visual inspection does not see; on a turbo the boost circuit is tested too. Beforehand, a German workshop recommends looking at the long-term fuel trims and comparing the requested boost pressure with the actual pressure.[1][2][4]
Does cleaning or replacing the MAF sensor fix P2279?
Normally not. Mechanic Base includes a faulty MAF sensor among the causes, but a German workshop explains that P2279 is a physical leak: a dirty MAF sensor gives a different code, P0101, and replacing it without checking the tightness only treats the symptom.[2][4]
Can a cracked intercooler cause P2279?
Yes. On an Audi A3 1.6 diesel documented by Mitchell 1, the P2279 was due to a cracked intercooler; it could not be seen with the naked eye and showed up when smoke was fed into the turbo intake.[1][4]
Does P2279 mean the same on all makes?
Yes, the definition is the same because it is a generic OBD-II code, but how you diagnose it changes depending on the engine: for Volkswagen 2.5 engines from 2005 to 2013, the manufacturer says to check the cam timing first.[5][6]
Will I pass the MOT with code P2279?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[7]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- SureTrack Real Fix: Smoking Out the CracksMitchell 1 · Technical documentation · consulted 2 October 2026
- What Does The P2279 Code Mean?Mechanic Base · Technical documentation · consulted 2 October 2026
- 18711/P2279/008825: Leak in Air Intake SystemRoss-Tech · Technical documentation · consulted 2 October 2026
- P2279 Luftleckage Saugrohr: Diagnose & RauchtestKFZ Dietrich · Other source · published 15 May 2026 · consulted 2 October 2026 · in German
- On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- TT 24-07-103: 2005-2013 Vehicles with 2.5L Engine - Fault Code P2279 Diagnostic TipVolkswagen Group of America · Manufacturer · published 9 September 2013 · consulted 2 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish