Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. 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.