OBDII diagnostic code P2176 means the Powertrain Control Module (PCM) has detected that the Throttle Body Actuator (TAC) has not learned the correct position in which the throttle valve should be in the throttle body. Therefore, the TAC system is limited in its function because of this error.
When this happens, the fail-safe mode or limp mode is activated, preventing the engine from normal acceleration until the malfunction is corrected and the code is cleared. The P2176 code is stored when other codes that indicate troubles in the safety of the engine or powertrain components are present.