Conditions for Setting the DTC

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The ECM detects a pressure change that is less than a calibrated amount.
Several tests must be completed to report a Fail with up to 17 hours between tests.