Diagnostic Aids
WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
Be sure DTC's P0C11, P0C12, P0C13, P0C14, P0C15 or P0C16 are not set. If any of these codes are set diagnose these first.