Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.
Using Toyota hand-held tester or scan tool, check for any other DTCs. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0121 is displayed, replace TP sensor.