Circuit Description
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
Electronic Throttle Control System (ETCS) uses throttle control motor to operate throttle valve. Throttle valve opening is detected by Throttle Position (TP) sensor which delivers input signals to Engine Control Module (ECM). ECM uses input signals and controls throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set if ECM malfunctions. If DTC P1633 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. Possible cause is defective ECM.