P2440: AIR valve stuck-open evidence comes from a closed-valve phase

P2440 concerns a secondary-air shut-off valve that appears to remain open. In the cited GM single-bank monitor, the revealing operating state is Phase 2: the AIR pump is commanded on while the valve is commanded closed. The controller evaluates the resulting pressure error rather than directly observing the valve's internal position.

The sequence makes the result meaningful

Phase 1 of the AIR diagnostic must already have passed, and Phase 2 requires more than 0.5 seconds of stability. Those prerequisites matter. An arbitrary pump-on pressure reading taken before the diagnostic sequence is not equivalent to the controlled closed-valve observation.

The failure criterion includes pressure error below a calibrated valve-error table or above 32 kPa. Because the lower boundary is table-based, this summary does not provide a single universal pressure number for condemning the valve.

Why a warm restart may prove little

This calibration requires more than 3,600 seconds of engine-off time, inlet air above 5°C and coolant between 5°C and 60°C. It runs once per trip when the AIR pump is commanded on. Conditional test weight exceeds two seconds and incorporates barometric pressure, airflow, supply voltage and ambient temperature factors.

A useful event record therefore links valve command, pump command, diagnostic phase and pressure response. Seeing the pump run or clearing the code does not establish that Phase 2 passed. The table supports a pressure-based stuck-open finding; it does not identify a particular mechanical obstruction, locate the valve or establish a part replacement without vehicle-specific checks.

Source and applicability

GM 2009 09OBDG07 Engine Diagnostics, single-bank secondary AIR application on physical page 124. This article does not extend its calibration to the separate dual-bank implementation or establish per-model fitment.

General Motors source, physical page 124