GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Throttle Position Sensor (TPS)

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OPERATION



The Throttle Position Sensor (TPS) is connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts from the VCM and the other to ground. A third wire is connected to the VCM to measure the voltage from the TPS. As the throttle valve angle is changed (accelerator pedal moved), the output of the TPS also changes. At a closed throttle position, the output of the TPS is low (approximately 0.5 volts). As the throttle valve opens, the output increases so that, at wide-open throttle, the output voltage should be approximately 4.5 volts. By monitoring the output voltage from the TPS, the VCM can determine fuel delivery based on throttle valve angle (driver demand).

TESTING



See Figures 1, 2 and 3

  1. Backprobe with a high impedance voltmeter at TPS ground terminal and 5 volt reference signal terminal.
  2.  
  3. With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
  4.  
  5. If the voltage is not as specified, either the wiring to the TPS or the VCM may be faulty. Correct any wiring or VCM faults before continuing test.
  6.  
  7. Backprobe with a high impedance voltmeter at the TP signal terminal and the sensor ground terminal.
  8.  
  9. With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
  10.  
  11. Verify that the TPS voltage increases or decreases smoothly as the throttle is opened or closed. Make sure to open and close the throttle very slowly in order to detect any abnormalities in the TPS voltage reading.
  12.  
  13. If the sensor voltage is not as specified, replace the sensor.
  14.  



Click image to see an enlarged view

Fig. Fig. 1: Common Throttle Position Sensor (TPS) wiring diagram (wire color, terminal identification/location may vary on certain models)



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Fig. Fig. 2: Using jumper wires and high impedance voltmeter, test between the sensor ground and reference terminals, the voltage should be approximately 5 volts



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Fig. Fig. 3: Next test between the sensor signal and ground terminals, verify that the TPS voltage increases or decreases smoothly as the throttle is opened or closed

REMOVAL & INSTALLATION



Except 1998-99 2.2L Engines

See Figure 4



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Fig. Fig. 4: Common Throttle Position Sensor (TPS)

  1. Disconnect the negative battery cable and remove the air cleaner and if equipped, the gasket and bracket.
  2.  
  3. Disengage the electrical connector.
  4.  
  5. Unfasten the two TPS attaching screw assemblies.
  6.  
  7. Remove the TPS from the throttle body assembly.
  8.  
  9. Remove the TPS seal.
  10.  

To install:
  1. Install the TPS seal over the throttle shaft.
  2.  
  3. With the throttle valve closed, install the TPS on the throttle shaft. Rotate it counterclockwise, to align the mounting holes.
  4.  
  5. Install the two TPS attaching screws. Tighten the screws to 18 inch lbs. (2 Nm).
  6.  
  7. Engage the electrical connector.
  8.  
  9. If equipped, install the bracket and gasket air cleaner and gasket.
  10.  
  11. Connect the negative battery cable.
  12.  

1998-99 2.2L Engines
  1. Disconnect the negative battery cable and remove the air cleaner outlet resonator.
  2.  
  3. Remove the throttle body assembly.
  4.  
  5. Unfasten the two TPS attaching screw assemblies.
  6.  
  7. Remove the TPS from the throttle body assembly.
  8.  

To install:
  1. With the throttle valve closed, install the TPS on the throttle body.
  2.  
  3. Install the two TPS attaching screws. Tighten the screws to 27 inch lbs. (3 Nm).
  4.  
  5. Install the throttle body.
  6.  
  7. Install the air cleaner outlet resonator.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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