P2279: Intake Air System Leak Bank 1
What to do
Expect a rough or uneven idle, hesitation, and worse fuel economy. The useful thing about this family of codes is that they narrow down where the leak is, so ask which of them is stored — it can point at a specific section of pipework rather than the whole intake. Ask for a smoke or pressure test rather than a visual inspection: cracks in the concertina hose after the airflow sensor often only open when the engine moves under load, and cannot be seen at idle.
What this code means
Air is entering the engine without being measured. This code and the three that follow it are the payoff to every lean-condition code in the corpus, because they say where.
P0171 says the mixture is lean. P2177 and P2187 say when it goes lean, which narrows it to a class of cause. These four narrow it to a section of pipework — and that is as close to a physical location as a fault code ever gets.
How the module can tell. Airflow is measured at one point and pressure at another, and the relationship between them, the throttle angle and the engine's speed is predictable. A leak changes that relationship in a way whose signature depends on which side of each measurement it sits, so comparing measured airflow against inferred airflow places the leak between one landmark and the next. P2280, P2281 and P2282 are those three sections.
This general code is set where a leak is detected but cannot be placed, or on vehicles that do not implement the localised versions.
The unglamorous list of usual suspects, which is short and mostly cheap: the concertina hose between airflow sensor and throttle body, which cracks in its folds and often only opens under engine movement; intake manifold gaskets; the crankcase ventilation hoses; the brake servo hose; the throttle body gasket; and on a turbocharged engine any of the charge pipework, where a leak is also a boost leak and shows up at P2262.
One caution worth carrying: a leak that only opens when the engine rocks on its mounts under load is invisible with the engine idling in a workshop, which is why some of these are found only by pressurising the intake rather than by inspection.
Likely causes
Start here
- Split or cracked intake hose · easy
- Leaking intake manifold gasket · moderate
- Disconnected or leaking vacuum hose · easy
- Faulty PCV valve or split hose · easy
Less common
- Leaking brake servo or servo hose · moderate
- Leaking throttle body gasket · easy
- Loose intake ducting clamp · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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