DTC P2279: Intake Air System Leak: General Description

The positive crankcase ventilation (PCV) system reduces hydrocarbons (HC). The PCV system recirculates the unburned air/fuel mixture (blow-by vapor) into the intake manifold where it is drawn into the engine and burned, thus reducing HC. If the PCV hose comes off while air is supplied mainly via the idle air control (IAC) valve with the throttle closed, the amount of air supplied to the engine is considerably more than the amount of air the IAC valve supplies.

The engine control module (ECM) estimates the amount of air supplied to the engine while the throttle valve is fully closed, and if the estimated amount is more than the upper limit, it detects a malfunction and a DTC is stored.