Caprice V8-265 4.3L VIN W MFI (1995)
Throttle Position Sensor: Description and Operation
Throttle Position (TP) Sensor
The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body and is one of the most important sensors for
engine/transmission control. The TP sensor has one end connected to 5 volts from the Powertrain Control Module (PCM) and the other to PCM ground.
A third wire is connected to the PCM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the
voltage output of the TP sensor also changes.
At a closed throttle position, the voltage output of the TP sensor is low (approximately 0.5 volt). As the throttle valve opens. the output increases so that
at wide open throttle, the output voltage should be near 5.0 volts.
By monitoring the output voltage from the TP sensor, the PCM can determine fuel delivery based on throttle valve angle (driver demand).
A broken or loose TP sensor can cause intermittent bursts of fuel from the injector and cause an unstable idle, because the PCM detects the throttle is
moving.
If the TP sensor circuit is open, the PCM will set a Diagnostic Trouble Code (DTC) 22. IF the TP sensor circuit is shorted, the PCM will interpret this
signal as wide open throttle and a DTC 21 will be set A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the
PCM will use a default value for TP sensor, and some vehicle performance will return.
