P2279 on BMW: Causes, Symptoms, Fix Cost

What does P2279 mean on a BMW?

P2279 means the ECU sees more air in the cylinders than the MAF measured, so unmetered air is entering downstream of the sensor and pushing fuel trims positive.

BMW 3-Series N54/N55 (E90/E92)

2007-2013

N54 plastic charge pipes crack at the throttle body flange, especially with a tuned car. N55 valve cover CCV/oil separators fail and pull crankcase vacuum into the intake.

What causes P2279 on a BMW?

Beyond the generic causes listed on the main P2279 page, these are the BMW-specific patterns we see most often:

BMW 3-Series N54/N55 (E90/E92)Cracked OEM plastic charge pipe (N54, part 11617599290)

BMW 3-Series N54/N55 (E90/E92)Failed oil separator in the valve cover (N55)

BMW 3-Series N54/N55 (E90/E92)Perished brake booster vacuum hose at the check valve

How to diagnose P2279 on a BMW with OBD2

Follow these steps to pinpoint the root cause of P2279:

Scan for all stored codes. P2279 usually shows up with P0171 and/or P0174, which confirm the lean condition.
Read live fuel trims at idle and at 2500 rpm. Strongly positive STFT at idle that normalizes at higher rpm points to a small vacuum leak.
Visually inspect the intake boot, flexing it and checking the underside where cracks often hide, plus the clamps at the MAF and throttle body.
Pull the oil filler cap at idle. If idle changes sharply or the cap sucks down hard, the PCV system needs attention.
Smoke test the intake tract with an EVAP smoke machine at 0.5 psi. Escaping smoke pinpoints the leak in minutes.
With the engine idling, spray carb cleaner or feed propane around suspect joints. An rpm change confirms leak location.
Inspect intake manifold seams, vacuum ports, and the brake booster hose for cracks, especially on plastic manifolds past 150,000 km.
Clear the code, drive a full warm-up cycle, and recheck fuel trims to confirm the repair took.

How much does P2279 cost to fix on a BMW? (EUR)

Estimated repair costs on a BMW (BMW parts and labour typically run 30% above the average for this code).

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Replace cracked intake boot or hose	€33–€117	€39–€104	€72–€221	Easy
Replace PCV valve and associated hoses	€20–€156	€52–€195	€72–€351	Easy
Replace intake manifold gasket	€52–€195	€325–€780	€377–€975	Professional
Replace vacuum lines or brake booster hose	€13–€78	€52–€156	€65–€234	Easy
Replace throttle body gasket	€20–€65	€104–€234	€124–€299	Moderate

Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.

These codes commonly cluster with P2279 on BMW vehicles:

P0171BMW P0174BMW P0101BMW P0106BMW P2187BMW

FAQ: P2279 on BMW

Can I tape up a cracked intake boot to get home?

Self-fusing silicone tape will hold for a day or two, but the crack keeps propagating with every vacuum pulse. A replacement boot is €25 to €90 and usually a 20 minute job with a screwdriver.

Why does my car idle rough but drive perfectly fine on the motorway?

Manifold vacuum is highest at idle when total airflow is lowest, so a pinhole leak makes up a big percentage of the air the engine sees. At cruise the same leak is a rounding error and closed-loop trims mask it.

Will P2279 damage anything if I keep driving?

The engine won't self-destruct, but sustained lean running raises combustion temps and cooks the catalytic converter over weeks. A new cat is €400 to €1500, so spending €50 on a hose is the smart play.

Can a dirty MAF sensor cause P2279 on its own?

No. P2279 specifically flags air the MAF never saw. A contaminated MAF typically sets P0101 or generic lean codes. Clean it with dedicated MAF spray if it looks oily, but don't stop looking after that.

Does a loose oil cap actually trigger P2279?

On many engines, yes. The oil cap seals the PCV circuit. If it's missing, cross-threaded, or the rubber seal is flat, you pull unmetered air straight into the crankcase and into the intake.

P2279 on BMW: Causes, Symptoms and Fix Cost