DTC P2172 OBDII indicates that the Powertrain Control Module (PCM) detected a malfunction in the Throttle Actuator Control (TAC) system. Specifically, the code means that unexpectedly an airflow above the set limit was encountered in the TAC system.
The throttle actuator is responsible for regulating the amount of air entering the engine via the accelerator pedal. It is held in the intake manifold by bolts sealed with a gasket. It is also connected to the vehicle’s computer through a wiring harness.