P1516, P2101, and P2176

WARNING: This page is about a different car, the 2009 GMC Sierra and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

DTCs P1516, P2101, and P2176 are Type A DTCs.
The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records.
The ECM commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions, the ECM commands the engine OFF.