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Randy
Randy, Auto Specialist
Category: GMC
Satisfied Customers: 9252
Experience:  25 Years Experience Automotive Technology.
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GMC Yukon Denali XL: I have a 2005 GMC Yukon Denali XL. The

Customer Question

I have a 2005 GMC Yukon Denali XL. The rear gate lock stopped unlocking. I took it apart and the actuator was clicking everytime I hit lock but made no sound when I hit unlock (With the door button or the key clicker ,fab). All the other doors unlocked.
I thought it was the actuator so I bought a new one from JCWhitney. When I plugged it in and tried it, it did the same thing. So....I think it has to me the signal coming from the front. I know there are fuses for the lock mode and the unlock mode but I would think that the fuses control all the locks, not just the back gate/window.
Where do I go from here?
Submitted: 1 year ago.
Category: GMC
Expert:  Randy replied 1 year ago.
Hi, my name is ***** ***** certified automotive professional with over 25 years experience. I will be glad to assist you with this.
I have included the liftgate diagrams for you. Check the ECC 10 amp fuse first, then suspect the liftgate lock relay((BEHIND RIGHT REAR QUARTER PANEL). The ECC 10 amp fuse is located in the Instrument Panel Fuse Box.
https://www.dropbox.com/s/psbywi1onzck210/2005%20GMC%20Yukon%206.0L%20Eng%20Denali.pdf?dl=0
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https://www.dropbox.com/s/x0b1g7nshz36uyz/LIFTGATE%20LOCK%20RELAY.pdf?dl=0
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Customer: replied 1 year ago.
What do I need to do to access the rear right quarter panel? I know where the instrument fuse panel is but How do I identify the ECC fuse?
Expert:  Randy replied 1 year ago.
https://www.dropbox.com/s/4g9gmlm72hq34rc/ip%20ecc%20fuse.png?dl=0
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https://www.dropbox.com/s/v22gikjuaexkzkb/REAR%20QUARTER%20%C2%AD.pdf?dl=0
Customer: replied 1 year ago.
Hi Randy. I followed the repair procedure and have voltage at the actuator on the lock command but no voltage at the unlock demand. The ECC fuse is good and there is 12v there. I switched the relays for the unlock and lock in the fuse box and had same results.
Lost now. thoughts?
Expert:  Randy replied 1 year ago.
I will check on this further for you.
Customer: replied 1 year ago.
Any more info?
Expert:  Randy replied 1 year ago.
This is the Circuit Description:
The body control module (BCM) internally grounds the lift gate lock relay control circuit for the lift gate lock relay when it receives a class 2 message from the driver door module (DDM), passenger door module (PDM), or when a lift gate lock function is activated. When the BCM grounds the lift gate lock relay control circuit the lift gate lock relay is energized and locks the lift gate.
Conditions for Setting the DTC:
1. The DTC will set if the lift gate lock relay control circuit is shorted to ground or open for more then one second.
Conditions for Running the DTC:
1. Battery voltage is between 9-16 volts.
2. The DTC will set if the lift gate lock function is active or inactive.
Action Taken :
1. If a short to ground is present on the liftgate lock relay control circuit, the liftgate lock relay will be energized and the liftgate lock actuator will be held in the lock position and will not unlock.
2. If an open condition is present on the liftgate lock relay control circuit, the liftgate will unlock but not lock.
3. The BCM will send a class 2 message to the driver information center (DIC) indicating that a fault has been detected and the DIC will display REPLACE LIFTGATE FUSE.
Diagnostic Aids:
1. An open ECC fuse
2. An open or short to ground in the lift gate lock relay battery positive voltage circuit
3. A faulty lift gate lock relay
4. An open or short to ground in the lift gate lock relay control circuit
5. A short to ground in the lift gate lock actuator lock control circuit will open the electronic climate control (ECC) with a lock command
6. A faulty BCM