Liftgate System Diagnosis (Power)
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Liftgate System Diagnosis (Power)
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Circuit/System Description
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The power liftgate system is a standard liftgate that has an added electric motor, hydraulic pump, a hydraulic arm, and an electric latch/cinch that can open and close the liftgate with no customer input. The liftgate can be both manually or automatically open and closed. Automatic opening or closing of the liftgate can be done through the interior liftgate switch, pushing either the open or close switch at the liftgate, or selecting open or close on the remote keyless transmitter. The automatic liftgate function can be disabled using the interior liftgate on/off control switch.
Power liftgate function will only be allowed if certain operating criteria are met. Any of the following may cause the power liftgate not to function:
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System voltage is below 10.5 V
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The vehicle doors are locked
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A liftgate control module DTC is set
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Liftgate motor excess current is detected which may be caused by a misaligned liftgate striker
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Interior trim and/or liftgate wedge/bumper misalignment
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A power liftgate that will not fully open may be caused by kinked or twisted hydraulic lines.
Whenever the liftgate control module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the liftgate control module.
An open or shorted accessory wake up ignition circuit between the engine control module and transmission control module will cause the power liftgate to work when the ignition is ON but not work when the ignition is OFF.
Schematic Reference
Liftgate Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Liftgate Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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Verify the K39 liftgate control module is programmed with the latest software.
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2.
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If the software is not the latest, program the K39 liftgate control module with the latest software. Refer to
Control Module References
for liftgate control module replacement, programming and setup.
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3.
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Verify the K39 liftgate control module does not have any current DTCs set.
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5.
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Verify DTC B2494 or B153F is not set as a history DTC.
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8.
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Verify the scan tool Liftgate Mode Switch parameter changes from 125 counts to 350 counts to 245 counts while rotating the S45B liftgate control switch - interior.
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10.
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Place the S45B liftgate control switch - interior to the OFF position.
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11.
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Verify the scan tool Liftgate Front Control Switch parameter changes between Inactive and Active while pressing and releasing the S45B liftgate control switch - interior.
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13.
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With the liftgate closed, observe the scan tool Liftgate Latch Pawl, Ratchet, and Sector Switch parameters. Each parameter status should be as listed below:
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Liftgate Latch Pawl Switch parameter - Closed
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Liftgate Latch Ratchet Switch parameter - Closed
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Liftgate Latch Sector Switch parameter - Inactive
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15.
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Verify the scan tool rear Liftgate Handle Switch parameter changes between Active and Inactive while pressing and releasing the S45A liftgate control switch-exterior.
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17.
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Using either the power door lock switches or the keyless entry transmitter, LOCK all doors then UNLOCK all doors. This will set the liftgate module door lock status to unlock.
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18.
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Verify the liftgate will manually open.
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20.
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With the liftgate open, verify the scan tool Liftgate Secondary Obstacle Detection parameter is 3V-3.5V
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22.
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With the liftgate open, verify the scan tool Liftgate Latch Pawl, Ratchet, and Sector Switch parameters are as listed below:
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Liftgate Latch Pawl Switch parameter - Open
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Liftgate Latch Ratchet Switch parameter - Open
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Liftgate Latch Sector Switch parameter - Inactive
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24.
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Observe the scan tool Liftgate Angle parameter while manually opening and closing the liftgate. The parameter should vary between 0° and approximately 80° as the liftgate opens and closes.
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26.
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Verify while manually opening and closing the liftgate is in proper aligned with the body bumpers, wedges and striker and there is no binding.
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27.
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Verify that the liftgate will remain at or near the full open position and does not drop down.
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28.
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If the liftgate will not remain open or drops, replace the liftgate gas strut. If the liftgate still drops after replacing the gas strut replace the M17 liftgate motor assembly, refer to
Liftgate Hydraulic Pump Replacement
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29.
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Verify the scan tool Liftgate Latch Sector Switch parameter changes from Inactive to Active then back to Inactive within 10 seconds while the liftgate is being automatically cinched closed.
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32.
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Verify the scan tool Liftgate Rear Close Switch parameter changes from Inactive to Active while pressing and releasing the B70 liftgate close switch.
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34.
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Liftgate open, select either the ¾ or Max position on the S45B liftgate control switch-interior then activate the power close function. Verify the liftgate power closes.
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36.
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Liftgate closed, activate the power open function. Verify the liftgate power opens.
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38.
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Verify the liftgate has not been auto reversing un-expectedly.
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39.
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If the liftgate has been auto reversing, check the following:
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Pump actuator hoses for twists or kinks
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Both liftgate object sensors for interference or deformity
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