Troubleshooting

P0121 - Throttle/Pedal Position Sensor/Switch"A"Circuit Range/Performance Problem

CIRCUIT DESCRIPTION

DTC Detecting Condition:

The throttle position sensor is mounted in the throttle body and detects the throttle valve opening angle.
When the throttle valve is fully closed, a voltage of approximately 0.7 V is applied to terminal VTA of the engine ECM. The voltage applied to the terminals VTA of the engine ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 3.5-5.0 V when the throttle valve is fully opened. The engine ECM judges the vehicle driving conditions from these signals input from terminal VTA, uses them as one of the conditions for deciding the air-fuel ratio correction, power increase correction and fuel-cut control etc.

Wiring Diagram:

Step 1:

INSPECTION PROCEDURE

HINT: Read freeze frame data using TOYOTA hand-held tester or OBDII scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.