Circuit Description
WARNING: This page is about a different car, the 2003 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
For circuit description, see CIRCUIT DESCRIPTION under DTCs P2120, P2122, P2123, P2125, P2127, P2128 OR P2138. DTC P2121 is set when difference between VPA and VPA2 is out of threshold and condition continues for .5 seconds. Possible cause is a faulty accelerator pedal position sensor.