P0010, P0013, P0020, P0023
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects an open in the CMP actuator solenoid circuits for greater than 4 seconds or a cumulative of 50 seconds, when the solenoid is commanded OFF.