Conditions for Setting the DTC: P0507
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects the actual idle speed is at least 200 RPM above the desired idle speed for greater than 19 seconds.