Jeep Wagoneer/Commando/Cherokee 1984-1998

Throttle Position (TPS) Sensor

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OPERATION



See Figure 1

The Throttle Position Sensor, or TPS is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine fuel delivery volume.

The TPS is a potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM 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 .5 volts). As the throttle valve opens, the output increases so that, at wide-open throttle, the output voltage should be above 3.9 volts.

By monitoring the output voltage from the TPS, the PCM can determine fuel delivery based on throttle valve angle (driver demand).



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Fig. Fig. 1: View of the Throttle Position (TPS) Sensor-1996 4.0L engine

TESTING



See Figures 2, 3 and 4

  1. With the key ON and engine OFF , backprobe with a high impedance voltmeter at the two end terminals of the TPS connector and battery ground. Verify that one terminal reads approximately 5.0 volts.
  2.  
  3. Backprobe with a high impedance ohmmeter between the end terminal that did not have the 5.0 volt signal and battery ground. Verify that the resistance is less than 5 ohms.
  4.  
  5. If the voltages are not as specified, either the wiring to the TPS or the PCM may be faulty. Correct any wiring or PCM faults before continuing test.
  6.  



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Fig. Fig. 2: Disengage the Throttle Position Sensor (TPS) wiring harness connector



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Fig. Fig. 3: Connect a voltmeter to the middle terminal of the TPS (A) and battery ground (B). With the throttle closed, note the reading



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Fig. Fig. 4: Check the voltage variation on the TPS while opening up the throttle to Wide Open Throttle (WOT)

  1. With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
  2.  
  3. 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.
  4.  
  5. If the sensor voltage is not as specified, replace the sensor.
  6.  

Removal & Installation



See Figures 5 and 6

  1. Remove the air intake tube at the throttle body.
  2.  
  3. Disengage the TPS wiring connector and remove the two mounting screws.
  4.  
  5. Carefully remove the TPS from the throttle body.
  6.  

To install:
  1. The throttle shaft end has a tang that can be fitted into the TPS two different ways. Only one of the installed positions is correct. When correctly positioned, the TPS can be rotated a few degrees. To determine correct positioning, place the TPS onto the throttle body with the throttle shaft tang on one side of the TPS socket. Verify that the TPS can be rotated. If the TPS cannot be rotated, place the TPS on the throttle body with the throttle shaft tang on the other side.
  2.  
  3. Tighten the two TPS mounting bolts to 60 inch lbs. (7 Nm) and engage the wiring connector.
  4.  
  5. Manually operate the throttle and check for any binding.
  6.  
  7. Install the air intake tube.
  8.  



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Fig. Fig. 5: Remove the throttle position sensor retainers ...



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Fig. Fig. 6: ... then, remove the throttle position sensor

 
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