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Diagnostic Test

  1. CHECK FOR ACTIVE DTCS 
    NOTE:

    This DTC will only set during the power open operation after the four second time out. This may make it difficult to reproduce.

    1. With the scan tool, record and erase DTCs.
    2. Cycle the ignition off, wait 10 seconds, then cycle the ignition on.
    3. Operate the power liftgate several times if possible.
    4. With the scan tool, read Active DTCs.

      Does the scan tool display; B1977-00-POWER LIFTGATE OPEN OPERATION - SECTOR SWITCH PERFORMANCE?

      Yes 

      • Go To  2

      No 

      • Using the wiring diagram/schematic as a guide, inspect the wiring and connectors for an intermittent condition. Operate the door several times and check for any binding or other obstructions.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  2. CHECK FOR A BINDING LIFTGATE 
    1. Examine the liftgate for proper fit and alignment, loose/hard or torn seals, misaligned latch striker or anything that would cause an obstruction to proper operation.
    2. Manually operate the liftgate of a known good vehicle and notice the effort needed to open and close.
    3. Compare the effort needed on the disabled liftgate.
    4. Especially notice the effort needed to unlatch and close the liftgate.

      Does it take more effort to operate the liftgate than it should?

      Yes 

      No 

      • Go To  3
  3. VERIFY THE LATCH HOME POSITION IN THE SCAN TOOL 
    1. Make sure the liftgate is closed.
    2. With the scan tool in Inputs/Outputs, read the "Sector Gear Switch Closed" state.

      Does the scan tool display; YES?

      Yes 

      • Go To  8

      No 

      • Go To  4
  4. CHECK THE POWER LIFTGATE LATCH 
    1. Disconnect the Power Liftgate Latch harness connector.
    2. With the scan tool, monitor the Sector Gear Switch Closed state.
    3. Connect a jumper wire between the (Q79) Sector Switch Sense circuit and the (Q901) Sensor Ground circuit.
    4. Repeat the previous step several times by disconnecting and connecting the jumper while observing the scan tool.

      Did the scan tool show the switch state changing correctly every time the jumper was connected and disconnected?

      Yes 

      • Replace the Power Liftgate Latch in accordance with the service information and using the scan tool, run the "Latch Home Sector Test". Refer to LATCH, LIFTGATE, REMOVAL .
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK THE (Q901) LOGIC GROUND CIRCUIT FOR AN OPEN 
    1. Cycle the ignition off.
    2. Cycle all lights off.
    3. Measure the resistance between ground and the (Q901) Logic Ground circuit.
    4. Wiggle the harness while observing the ohmmeter.

      Is the resistance below 9.5 Ohms?

      Yes 

      • Go To  6

      No 

      • Repair the (Q901) Logic Ground circuit for an open.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  6. CHECK THE (Q79) SECTOR SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND 
    1. Measure the resistance between the (Q901) Logic Ground circuit and the (Q79) Sector Switch Sense circuit.
    2. Wiggle the harness while observing the ohmmeter.

      Is the resistance below 100.0 Ohms?

      Yes 

      • Go To  10

      No 

      • Go To  7
  7. CHECK THE (Q79) SECTOR SWITCH SENSE CIRCUIT FOR AN OPEN 
    1. Disconnect the Power Liftgate Module C2 harness connector.
    2. Measure the resistance of the (Q79) Sector Switch Sense circuit between the Power Liftgate C2 harness connector and the Power Liftgate Latch harness connector.
    3. Wiggle the harness while observing the ohmmeter.

      Is the resistance below 2.0 Ohms?

      No 

      • Repair the (Q79) Sector Switch Sense circuit for an open.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      Yes 

      • Go To  8
  8. CHECK THE (Q79) SECTOR SWITCH SENSE CIRCUIT FOR A SHORT TO VOLTAGE 
    1. Cycle the ignition on.
    2. Measure the voltage of the (Q79) Sector Switch Sense circuit.
    3. Wiggle the harness while observing the voltmeter.

      Is there any voltage present?

      No 

      Yes 

      • Repair the (Q79) Sector Switch Sense circuit for a short to voltage.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  9. ADJUST LATCH TO HOME POSITION 
    1. Close the liftgate.
    2. With the scan tool run the "Latch Home Sector Test".
      NOTE:

      This test will try to adjust the sector gear to the Home Position.

    3. With the scan tool in Inputs/Outputs, read the "Sector Gear Switch Closed" state.

      Does the scan tool display: NO?

      Yes 

      • Repair is complete. The latch was not in the Home position.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Go To  10
  10. CHECK THE (Q79) SECTOR SWITCH SENSE CIRCUIT FOR A SHORT TO THE (Q901) LOGIC GROUND CIRCUIT 
    1. Disconnect the Power Liftgate Latch harness connector.
    2. Measure the resistance between the (Q901) Logic Ground circuit and the (Q79) Sector Switch Sense circuit.
    3. Wiggle the harness while observing the ohmmeter.

      Is the resistance below 1, 000 Ohms?

      Yes 

      • Repair the (Q79) Sector Switch Sense circuit for a short to ground.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

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