Sub-Throttle Position (Sub-TP) Sensor: Inspection
WARNING: This page is about a different car, the 1997 Lexus SC 400. However, it is still accessible from the selected car via links, so may be relevant.
Check sub-TP sensor resistance. See SUB-THROTTLE POSITION (SUB-TP) SENSOR under FUEL SYSTEM in SPECIFICATIONS article. If resistance is not as specified, adjust sub-TP sensor.