GM Corsica/Beretta 1988-1996 Repair Guide

Throttle Position Sensor (TPS)



The TP sensor is mounted to the throttle body, opposite the throttle lever and is connected to the throttle shaft. Its function is to sense the current throttle valve position and relay that information to the PCM. Throttle position information allows the PCM to generate the required injector control signals. The TP sensor consists of a potentiometer which alters the flow of voltage according to the position of a wiper on the variable resistor windings, in proportion to the movement of the throttle shaft.


Except 1996 2.2L Engines and 1994-96 3.1L Engines

See Figure 1

  1. Visually check the connector, making sure it is connected properly and all of the terminals are straight, tight and free of corrosion.
  3. Connect a voltmeter to a known good engine ground and TPS terminal A (reference signal). Turn the ignition switch to the ON position to check the reference voltage:
    1. If 4.5-5.5 volts are present at terminal A, proceed to the next step.
    3. If the voltage is outside of specifications, check the reference circuit.

  5. Connect a voltmeter to the TPS connector terminal C (TPS signal voltage) and to terminal B (sensor ground).
  7. Turn the ignition switch to the ON position, with the engine OFF .
  9. Check the TPS voltage with the throttle in the fully closed position, then operate the throttle to the full open position, while watching the voltmeter.

Click image to see an enlarged view

Fig. Fig. 1: Throttle Position (TP) sensor circuit - except 1996 2.2L Engines and 1994-96 3.1L Engines

  1. For 2.0L, 2.2L, 2.8L and 3.1L engines, note the following:
    1. If the voltage at closed throttle is 0.2-0.9 volts and has a smooth increase to 4.5-4.7 volts when the throttle is fully open, the TPS is operating normally.
    3. If