Diagnostic Aids
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.
A C0131 can get set if the ECU is loosely attached to the hydraulic unit. The mountings should be checked for the proper torque.