Envoy, Rainer, Trailblazer 2006-2007

Accelerator Pedal Position Sensor

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Operation



4.2L Engine

The APP sensor is mounted on the accelerator pedal assembly. The APP is actually 2 individual APP sensors within one housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.

5.3L And 6.0L Engines

The accelerator pedal contains 2 individual accelerator pedal position (APP) sensors within the assembly. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:



A 5-volt reference circuit
 
A low reference circuit
 
A signal circuit
 

The APP sensors are used to determine the pedal angle. The engine control module (ECM) provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors provide the ECM with signal voltage proportional to the pedal movement. The APP sensor 1 signal voltage at rest position is less than 1 volt and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position above 4 volts and decreases as the pedal is actuated.

Removal & Installation



4.2L Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the accelerator pedal position (APP) sensor electrical connector.
  4.  
  5. Remove the APP sensor retaining fasteners.
  6.  
  7. Remove the APP sensor (2) from the vehicle.

    Click image to see an enlarged view

    Fig. Location of the accelerator pedal position (APP) sensor (2)

  8.  

To install:

  1. Install the APP sensor (2) to vehicle.
  2.  
  3. Install the APP sensor retaining fasteners (1) and tighten to 89 inch lbs. (10 Nm).
  4.  
  5. Connect the APP sensor electrical connector.
  6.  
  7. Connect the negative battery cable.
  8.  

5.3L And 6.0L Engines
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the accelerator pedal position (APP) sensor electrical connector.
  4.  
  5. Remove the 3 APP sensor bolts (1).
  6.  
  7. Remove the APP sensor (2).
  8.  

To install:

  1. Install the APP sensor.
  2.  
  3. Install the 3 APP sensor bolts (1) and tighten to 15 ft. lbs. (20 Nm).
  4.  
  5. Connect the APP sensor electrical connector.
  6.  
  7. Verify that the vehicle meets the following conditions:

    The vehicle is not in a reduced engine power mode
     
    The ignition is ON
     
    The engine is OFF
     

  8.  
  9. Connect a scan tool in order to test for a proper throttle-opening and throttle-closing range.
  10.  
  11. Operate the accelerator pedal and monitor the throttle angles. The accelerator pedal should operate freely, without binding, between a closed throttle, and a wide open throttle.
  12.  
  13. Connect the negative battery cable.
  14.  

Testing





Click image to see an enlarged view

Fig. Accelerator Pedal Position (APP) sensor electrical connector end view

4.2L Engine
  1. Turn OFF the ignition.
  2.  
  3. Disconnect the Accelerator Pedal Position (APP) sensor electrical connector.
  4.  
  5. Disconnect the Powertrain Control Module (PCM).
  6.  
  7. Use a Digital Multi-Meter (DMM) to measure the resistance of the following circuits for each of the APP sensors:

    The low reference circuit
     
    The signal circuit
     
    The 5-volt reference circuit
     

  8.  
  9. If any of the circuits measure more than 5 ohms, repair the high resistance in the circuit. If any of the circuits measure less than 5 ohms, continue to the next step.
  10.  
  11. Test for a short between any of the circuits in the APP sensor harness and repair the circuit as necessary.
  12.  
  13. If no short exists, replace the APP sensor.
  14.  
  15. Using a scan tool, clear the DTCs.
  16.  
  17. Turn OFF the ignition for 30 seconds.
  18.  
  19. Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.
  20.  
  21. If the DTC doesn't fail this ignition, observe the Capture Info with a scan tool and check for any undiagnosed DTCs.
  22.  

5.3L And 6.0L Engines
  1. Turn OFF the ignition.
  2.  
  3. Disconnect the Accelerator Pedal Position (APP) sensor electrical connector.
  4.  
  5. Disconnect the Engine Control Module (ECM).
  6.  
  7. Use a Digital Multi-Meter (DMM) to measure the resistance of the following circuits for each of the APP sensors:

    The low reference circuit
     
    The signal circuit
     
    The 5-volt reference circuit
     

  8.  
  9. If any of the circuits measure more than 5 ohms, repair the high resistance in the circuit. If any of the circuits measure less than 5 ohms, continue to the next step.
  10.  
  11. Test the signal circuit of APP sensor 1 for a short to the signal circuit of the APP sensor 2.
  12.  
  13. If no short exists, test for an intermittent and for a poor connection at the APP sensor.
  14.  
  15. If no intermittent or poor connection exists at the APP sensor, test for an intermittent and for a poor connection at the ECM.
  16.  
  17. If no intermittent or poor connection exists at the ECM, replace the APP sensor.
  18.  
  19. Using a scan tool, clear the DTCs.
  20.  
  21. Turn OFF the ignition for 30 seconds.
  22.  
  23. Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.
  24.  
  25. If the DTC doesn't fail this ignition, observe the Capture Info with a scan tool and check for any undiagnosed DTCs.
  26.  

 
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