P2279 on Audi: How to Diagnose & Fix
Intake Air System Leak
2 Audi models · 2 documented issues · $300-$900 repair
P2279 on Audi by model: symptoms, diagnosis and fix
The supercharged 3.0 TFSI's crankcase ventilation module (PCV / air-oil separator) uses an internal diaphragm that hardens and tears. When it does, the engine pulls unmetered air through the crankcase, gives up its ability to control crankcase pressure, and starts drawing oil into the intake. Owners typically see it between roughly 60,000 and 80,000 miles. Symptoms overlap with several other faults, which is why it is so often misdiagnosed - the tell is a rough or hunting idle combined with rising oil consumption and lean/crankcase-ventilation fault codes. Excess crankcase pressure also pushes oil past the rear main and cam seals, so a neglected PCV can create leaks that look like a much bigger problem.
Common Symptoms
- Rough, hunting or unstable idle
- Increased oil consumption with no visible external leak
- Blue smoke on startup or under load
- Whistling or hissing from the top of the engine
- Oil smell in the engine bay; oil pushed past cam or rear main seals
How to Fix
No recall. Replace the PCV / air-oil separator module with the current revised part number (Audi went through several revisions) along with its gaskets; the module sits beneath the supercharger, so the supercharger has to come off to reach it. A smoke test or a crankcase-vacuum measurement at the oil filler confirms the diagnosis before parts are thrown at it. Replacing seals that were pushed out by crankcase pressure without fixing the PCV guarantees the leak returns.
Sources for this issue (3)
Audi TSB 2040644/6 covers a metallic whistling or grinding sound at warm idle, a sporadic MIL and possible P2279 or P0507 on 4.0 TFSI vehicles. A leak in the crankcase breather pressure-regulating module can cause the condition. Audi’s labor table explicitly includes the S8.
Common Symptoms
- Metallic whistle or grinding sound at warm idle
- Sporadic MIL with P2279 or P0507
How to Fix
Compare the sound with Audi’s reference condition and check whether opening the oil filler cap changes it. Read P2279/P0507 and rule out other intake leaks. When the sound matches and is affected by the filler-cap check, follow Audi’s oil-separator breather replacement procedure and renew required seals/consumables by VIN. Do not diagnose by oil-cap feel alone.
Sources for this issue (1)
P2279 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P2279 mean on a Audi?
P2279 stands for "Intake Air System Leak." This code means the engine computer detected an air leak in the intake system downstream of the mass airflow sensor (unmetered air entering the engine). Because this air is not measured, the engine may run lean, idle roughly, or behave inconsistently. The computer flags it when fuel trims or airflow readings indicate more air is reaching the cylinders than the sensor accounts for. It is usually not an immediate safety issue but can cause drivability problems, poor fuel economy, and other related lean codes. On Audi it is documented across 2 models: S4, S8.
What are the most common causes of P2279?
The most common causes of P2279 are: Cracked or loose intake hose / air duct after the MAF, Vacuum leak (hoses, gaskets, PCV), Loose or damaged intake manifold gasket, Faulty or dirty mass airflow sensor, Leaking throttle body gasket, Unseated or cracked intake boot clamp, Failed PCV valve or hose. The specific cause varies by vehicle.
How much does it cost to fix P2279 on a Audi?
Published repair estimates on Audi range from $300 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.