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Jerry, Master Mechanic
Category: GM
Satisfied Customers: 17220
Experience:  ASE Master tech, 30 years experience GM certified
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GM Yukol XL Denali: I have a 2007 Yukon xl denali. The power

Customer Question

I have a 2007 Yukon xl denali. The power liftgate, when actuated, raises the liftgate several inches and then reverses, closes and locks. Just prior to this it had lifted almost fully, then you could hear what sounded like gear teeth stripping over each other before disengaging completely. I have opened the trim covering the motor and disconnected the arm to the gate. Even under no load, the lifting arm only moves about 15 degrees and then returns to closed. What triggers the unit to return to closed?
Submitted: 2 years ago.
Category: GM
Expert:  Jerry replied 2 years ago.
Hello. My name is ***** ***** you for using the site, I will be happy to assist you today.
There has been a factory service bulletin, (not a recall) for that type of concern. The control module may also need to be calibrated with a scan tool after the repair.
Here is a link to what it states.
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Customer: replied 2 years ago.
Jerry, I read the bulletin and opened up the headliner and found no damaged or abraided wires. I also removed the motor assembly from the body, disconnected the arm that ties the motor assembly to the rear hatch and cycled the unit, Same problem. I removed the return spring and opened up the worm gear drive and couldn't find a problem. Your answer didn't address the grinding gear noise I mentioned. What you did note was that the unit can be recalibrated. I wonder if that's what I need. Is the scan tool you mentioned something worth buying? Do most mechanics have this? Is this exclusively a dealer service? Thanks, Bill
Expert:  Jerry replied 2 years ago.
The grinding sounds could just be inside the motor but the scan tool is about $2500 at the least. Most shops will have one and a GM dealership will always have at least one.
IMPORTANT: To ensure proper calibration of the liftgate, the liftgate assembly must be at room temperature during calibration.
Use this procedure after replacing, repairing, or disassembling any portion of the power liftgate assembly.
Calibrate Liftgate
Connect the Tech 2 to the vehicle.
Select Special Functions in the Liftgate Module menu.
Select LGM Open/Close Test.
Follow the on screen instructions.
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