P0121 Fault Diagnosis and Fix for 2004 Toyota Tacoma 4WD with V6 Engine
I own a 2004 Toyota Tacoma with 4WD and a 3.4-liter V6 engine. Yesterday afternoon, while driving around town, I experienced sudden accelerator malfunction — the gas pedal felt unresponsive until nearly halfway to the floor, after which the engine began over-revving. My OBD-II diagnostic tool shows fault code P012
According to Toyota Technical Service Bulletin (TSB), for P0121 - Throttle Pedal Position Sensor/switch 'A' Circuit Range/Performance issue in the 2004 Tacoma: INSPECTION PROCEDURE HINT: Use a hand-held tester or OBD-II scan tool to review freeze frame data. This records engine conditions at the time of malfunction — including whether the vehicle was running or stopped, if the engine was warm, and air-fuel ratio (lean/rich). Step 1: Check for any additional diagnostic trouble codes (DTCs) besides P0121. - If yes, refer to the relevant DTC chart (page DI−322). - If no, replace the throttle position sensor as the most likely cause.