Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

DTCs P0121 is a Type B DTC.
DTCs P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2 and P2135 are Type A DTCs.
The ECM commands the throttle actuator control (TAC) system to operate in a Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions, the ECM commands the engine OFF.