Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Throttle/pedal position sensor/switch ”a” circuit range/performance problem / Circuit description

Toyota Corolla (E120): Circuit description

Refer to dtc p0120

Dtc no.	Dtc detection condition	Trouble area
P0121	The following condition is met 4 times. After the vehicle speed has exceeded 19 mph (30 km/h) once, the throttle position sensor output value is out of normal range when the throttle valve is closed at 0 km/h	Throttle position sensor (built in throttle body)

Monitor description

The throttle position sensor varies its resistance with the angle of the throttle valve. The ecm applies a regulated reference voltage to the throttle position sensor “+” terminal and calculates the angle of the throttle valve based on the voltage present at the throttle position sensor “signal” terminal.

When the throttle valve is near the fully closed position, the output voltage of the throttle position sensor is low. When it is near the fully open position, the output voltage is high.

The ecm checks the indicated angle of the throttle valve during “stop and go” conditions. If the indicated angle (or voltage) in the “closed throttle” position is out of the specified range, the ecm interprets this as a malfunction in the throttle position sensor and sets a dtc.

Monitor strategy

Typical enabling condition

”Stop and go” is defined as follows: ”stop” indicates a vehicle speed of 0 mph (0 km/h). ”Go” indicates a vehicle speed of 18.6 Mph (30 km/h).

Typical malfunction thresholds

Component operating range