Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2008 Pontiac G5 and 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

DTCs P2120, P2122, P2123, P2125, P2127, P2128, and P2138 are Type A DTCs.
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.