Seville V8-273 4.5L (1989)
Throttle Position Sensor: Description and Operation
Throttle Position Sensor
The Throttle Position Sensor (TPS) is a three wire sensor or potentiometer which has a five volt reference, a reference ground, and a output signal from
the sensor to the Electronic Control Module (ECM). The sensor output signal is a DC voltage that varies with throttle angle. As the throttle valve angle
changes, the voltage output of the TPS also changes. At a closed throttle position, the output of the TPS is low. As the throttle plate opens, the output
voltage increases so that, at wide-open throttle, the output voltage should be approximately 5 volts.
By monitoring the output voltage from the TPS, the ECM can modify fuel delivery based on throttle valve angle. For example, power enrichment occurs
when the throttle angle approaches wide open throttle. The ECM senses changes in TPS output which controls fuel delivery. Acceleration enrichment
occurs when the throttle angle increases abruptly, similar to an accelerator pump on a carbureted vehicle.
The TPS can either be misadjusted, open, or shorted. If the sensor is open, the ECM will sense that the throttle is closed, and performance will be
reduced. This will normally set a trouble code E022. If the switch is shorted, the ECM will sense that the vehicle is at WOT, and a trouble code E021
will be set. Once a trouble code is set, the ECM will substitute a value for the TPS, and some vehicle performance will return.
