Prizm L4-1800cc 1.8L DOHC (1993)
Throttle Position Sensor: Description and Operation
Throttle Position Sensor (TPS) Operation
The Throttle Position Sensor (TPS) is a potentiometer that is mounted to the throttle body.
The TPS is a three wire sensor with a referance voltage, a ground provided by the PCM, and a sensor output signal to the PCM. The sensor output signal
is a DC voltage that varies with throttle angle.
The PCM supplies a five-volt signal to the sensor through a resistor in the PCM and measures the signal voltage. As the throttle angle is changed
(accelerator pedal moved), the output of the sensor also changes. At closed throttle, the out put voltage is low. As throttle angle increases, the output
increases so that, at wide open throttle, the output approaches 5 volts.
By monitoring the output voltage of the TPS, the PCM can modify fuel delivery based on throttle angle.
The TPS also houses an idle switch. The PCM supplies both ignition voltage and a ground to the idle switch. When the throttle is closed, the PCM senses
the voltage drop caused by the switch closed to ground. The PCM uses this information as a reference for idle air control operation.
A failure in the TPS sensor circuit should set a Diagnostic Trouble Code (DTC) 41.
