GM Cavalier/Sunbird/Skyhawk/Firenza 1982-1994

Throttle Position (TP) Sensor

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OPERATION



See Figure 1

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 ECM. Throttle position information allows the ECM 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. As throttle angle is changed (the accelerator is pressed down), the output of the sensor changes.



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Fig. Fig. 1: The Throttle Position (TP) sensor is mounted to the throttle body

At closed throttle, the output of the sensor is fairly low (0.5 V). As the throttle opens, the output voltage should rise towards 5 V. By monitoring the sensor output voltage, the control module can determine fuel delivery based on throttle angle.

TESTING



  1. Remove air cleaner.
  2.  
  3. Disconnect TP sensor harness from the sensor.
  4.  
  5. Using three jumper wires, connect the TP sensor harness to then sensor.
  6.  
  7. With ignition ON and the engine stopped, use a digital voltmeter to measure voltage between the bottom and middle terminals.
  8.  
  9. Voltage should read 0.450-1.250 volts.
  10.  

ADJUSTMENT



The TP sensor is not adjustable on most models. Adjustable TP sensors have elongated mounting holes to allow adjustment.

  1. If necessary, remove the EGR valve and heat shield from engine.
  2.  
  3. Using three 6 in. (152mm) jumpers, connect the TP sensor harness to the TP sensor.
  4.  
  5. With ignition ON , engine stopped, use a digital voltmeter to measure voltage between the bottom and middle terminals.
  6.  
  7. Loosen the two TP sensor attaching screws and rotate the sensor to obtain a voltage reading of 0.450-1.250 volts.
  8.  
  9. With the ignition OFF , remove the jumpers and reconnect TP sensor harness to TP sensor.
  10.  
  11. Install the EGR valve and heat shield to engine, using new gasket as necessary.
  12.  
  13. Install the air cleaner gasket and air cleaner to throttle body unit.
  14.  

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Detach the TP sensor electrical connector.
  4.  
  5. Unfasten the sensor attaching screws and retainer, then remove the TP sensor from the vehicle. If installing a new sensor, discard the screws. New ones are supplied in the service kit.
  6.  

To install:
  1. With the throttle valve in the closed (idle) position, install the TP sensor on the throttle body assembly.
  2.  

When installing the TP sensor, always use new attaching screws.

  1. Secure the sensor using the retainers and two new attaching screws. Tighten the screws to 18 inch lbs. (2 Nm).
  2.  
  3. Attach the TP sensor electrical connector.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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