GM Cavalier/Sunfire 1995-2000 Repair Guide

Throttle Position Sensor

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OPERATION



The Throttle Position (TP) sensor is a potentiometer that provides a signal to the PCM that is directly proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and transmits an appropriate electrical signal to the PCM. These signals are used by the PCM to adjust the air/fuel mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The TP sensor is not adjustable.

The TP sensor receives a 5 volt reference signal and a ground circuit from the PCM. A return signal circuit is connected to wiper that runs on a resistor internally on the sensor. The further the throttle is opened, the wiper moves along the resistor, at wide open throttle, the wiper essentially creates a loop between the reference signal and the signal return returning the full or nearly full 5 volt signal back to the PCM. At idle the signal return should be approximately 0.9 volts.

TESTING



See Figures 1, 2, 3, 4 and 5



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Fig. Fig. 1: Testing the signal circuit to the TP sensor



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Fig. Fig. 2: Testing the signal return circuit of the TP sensor



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Fig. Fig. 3: Testing the ground circuit of the TP sensor



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Fig. Fig. 4: Testing the operation of the potentiometer inside the TP sensor while slowly opening the throttle



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Fig. Fig. 5: The TP sensor can be monitored with an appropriate and Data-stream capable scan tool

  1. With the engine OFF and the ignition ON , check the voltage at the signal return circuit of the TP sensor by carefully backprobing the connector using a DVOM.
  2.  
  3. Voltage should be between 0.2 and 1.4 volts at idle.
  4.  
  5. Slowly move the throttle pulley to the wide open throttle (WOT) position and watch the voltage on the DVOM. The voltage should slowly rise to slightly less than 4.8v at Wide Open Throttle (WOT).
  6.  
  7. If no voltage is present, check the wiring harness for supply voltage (5.0v) and ground (0.3v or less), by referring to your corresponding wiring guide. If supply voltage and ground are present, but no output voltage from TP, replace the TP sensor. If supply voltage and ground do not meet specifications, make necessary repairs to the harness or PCM.
  8.  

REMOVAL & INSTALLATION



See Figures 6, 7, 8, 9 and 10



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Fig. Fig. 6: TP sensor mounting-2.4L engine



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Fig. Fig. 7: Unplug the TP sensor connector



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Fig. Fig. 8: Remove the two retaining bolts and ...



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Fig. Fig. 9: ... remove the sensor from the throttle body



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Fig. Fig. 10: Align the throttle shaft with the TP sensor before installation

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner outlet tube.
  4.  
  5. Unplug the electrical connection.
  6.  
  7. Remove the two retaining screws and remove the sensor from the throttle body.
  8.  

To install:
  1. With the throttle plate full closed, carefully slide the rotary tangs on the sensor into position over the throttle shaft, then rotate the sensor counterclockwise to the align the bolt holes..
  2.  


CAUTION
Failure to install the TP sensor in this manner may result in sensor damage or high idle speeds.

The TP sensor is not adjustable.

  1. Install and tighten the sensor mounting screws to 18-35 inch lbs. (2-4 Nm).
  2.  
  3. Connect the wiring harness to the sensor.
  4.  
  5. Iinstall the air intake resonator.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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