Action Taken When the DTC Sets

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban, and 2018 Cadillac Escalade ESV. 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.