GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

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 ECM and the other to ground.

A third wire is connected to the ECM 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 ECM can determine fuel delivery based on throttle valve angle (driver demand).

TESTING



See Figures 1, 2, 3, 4 and 5

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Fig. Fig. 1: Throttle Position Sensor (TPS) wiring diagram-2.3L engine



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Fig. Fig. 2: Throttle Position Sensor (TPS) wiring diagram-2.5L engine



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Fig. Fig. 3: Throttle Position Sensor (TPS) wiring diagram-3.1L engine



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Fig. Fig. 4: Throttle Position Sensor (TPS) wiring diagram-3.4L engine



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Fig. Fig. 5: Throttle Position Sensor (TPS) wiring diagram-3.8L engine

  1. For all engines except the 3.8L, backprobe with a high impedance voltmeter at TPS terminals A and B .
  2.  
  3. For the 3.8L engine, backprobe with a high impedance voltmeter at TPS terminals A and C .
  4.  
  5. With the key ON and engine OFF, the voltmeter reading should be approximately 5.0 volts.
  6.  
  7. If the voltage is not as specified, either the wiring to the TPS or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
  8.  
  9. Backprobe with a high impedance voltmeter at terminals C and B .
  10.  
  11. With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
  12.  
  13. 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.
  14.  
  15. If the sensor voltage is not as specified, replace the sensor.
  16.  

REMOVAL & INSTALLATION



See Figure 6

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Fig. Fig. 6: Throttle Position Sensor (TPS) mounting

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary, remove the air cleaner assembly along with the necessary duct work.
  4.  
  5. Unfasten the TPS attaching screws. If the TPS is riveted to the throttle body, it will be necessary to drill out the rivets.
  6.  
  7. Remove the TPS from the throttle body assembly. If equipped, inspect the TPS O-ring and replace if necessary.
  8.  


WARNING
The throttle position sensor is an electrical component and should not be immersed in any type of liquid solvent or cleaner, as damage may result.

To install:
  1. With the throttle valve closed, install the TPS onto the throttle shaft. Rotate the TPS counterclockwise to align the mounting holes. Install the retaining screws or rivets. Tighten the retaining screws to 18 inch lbs. (2.0 Nm).
  2.  
  3. Install the air cleaner assembly and connect the negative battery cable.
  4.  

 
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