DTC P1121: Electric Throttle Control Actuator: Description
WARNING: This page is about a different car, the 2002 Nissan Maxima and 2002 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.
Electric throttle control actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The throttle control motor is operated by the ECM, and it opens and closes the throttle valve. The TP sensor detects the throttle valve position, the opening and closing speed of the throttle valve, and feeds the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals, and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition.