Conditions for Running the DTC

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0454 runs only when the engine-off natural vacuum small leak test, P0442, executes.
This test can run once per engine-off period. The length of the test can be up to 40 minutes.