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DTC P0121: THROTTLE POSITION (TP) SENSOR "A" CIRCUIT RANGE/PERFORMANCE FAULT Lexus LS III

CAUTIONIf ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION.

Circuit Description

The TP sensor is a dual variable resistor sensor that monitors throttle opening and TP sensor malfunction. Based on TP sensor signal, ECM determines vehicle driving condition and uses and uses throttle control motor to set throttle angle accordingly. DTC is set when VTA and VTA2 circuit voltage on TP sensor is out of range for 2 seconds. Possible cause is; faulty TP sensor.

Diagnostic Aids

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.