Circuit/System Verification
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Allow the engine to cool. Monitor the Cold Startup parameter, this should indicate Yes. Start and idle the engine for at least 2 minutes. DTC P1400 should run and pass.