I am new to this site but came here in the past to trouble shoot issues.
I have a yellow 06' H2 that has a series of minor issues over the past months I have had to work through.
I didn't find any useful info on the site to address this sited issues so I am including my results as an attempt to help others with similar issues.
First of all, in diagnosing the rear deck failing to operate with the door switch or key fob you should first check and see that the fuse is good. The instrument fuse block (IP)is where it is located. It is labeled as "LGATE".
That confirmed, the next issue to determine is if the RELAY that links the deck actuator is operable. This relay is located INSIDE the "B" column on the passenger side. Easy to get to. Remove the front and rear plastic sill covers (pull UP - no screws ). Then remove the upper cover on the pillar cover and extract teh one screw that secures it at the very top. Then this cover can be removed. You will need to pop out the courtesy light and work it through the cover to free the pillar cover completely.
Once removed, you can extract the small relay from inside the B column and inspect it for operation. It has 5 tabs/wires. If you scrape off teh foam padding from the body you can read teh schematic and see what this Omron relay does. It reverses the polarity to achieve teh "Lock-Unlock" function.
check the relay COIL tabs with a VOM and you could read between 70'ish and 90'ish ohms resistance. The coil is the two outer tabs on the group of 3 smaller spades. (White wire and one of two orange wires feed this. The center tab (black wire) is a ground. The 2'nd orange wire (B+) and the grey wires populate the two larger tabs. Be sure and ring continuity with the VOM to the large ground lug bolted to the B column as well. If all appears to be in order then it is time for the real task!
GM, in their infinite wisdom, chose not to have a manual deck override, an inner latch handle or even an access panel to assist in opening the rear deck should the actuator fail! Thanks Hummer division! Actually, despite the daunting task, the ability to get the rear deck open so the trim can be removed and gain access to the actuator is not as hard as it seems at first glance.
Clear out the rear area and fold up the third row jump seat. Start wherever your fingers succeed and pull out on the one piece rear trim. It is very tight quarters so go slow and work your way around the peremiter of the trim jerking just hard enough to get the snap in latches to release. There are plenty of them so take your time.
Once the top and both sides are clear then pull back on the trim in the center of the lower section below the glass. You must be able to work your hand and arm down past the wiper motor and find the actuator plate. This plate has 3 pull wires. One is the remote to the actual outer handle. Pulling this lower wire does nothing as the Delphi lock assy. is in free wheel when locked. You are after the two other upper cables. They are on opposite sides of the actuator plate. You will need to pull out on these 2 wires at about the same time as the deck lid has two latch assemblies on opposite sides. Keep tension against the deck lid and when both cables are pulled out the deck lid will move out slightly and it is now free to be opened ( Finally !)
Raise the deck lid and continue the trim removal. There is a single small bolt that secures the pull strap. Once that is removed the trim is free to be popped off completely.
Before you remove the actuator plate check the wiring for power when activated by the switch or fob. Remove the blue lock from the 2 wire connector and the remove the actual connector from the actuator. Using a VOM set on Volts check and see if you get a pulse of 12 volt power when you operate the fob. If you have a digital meter you will have to watch closely as the pulse is short and the digital meter sample rate is relatively slow to respond.
Watch closely ..... but what you are after is to see the Polarity change. Most digital meters will show some sort of brief garbage reading but you will likely be able to see the "-" appear in one of the two fob activation directions.
This is good news! If you have this condition you wiring is likely OK as is your voltage to the actuator.
I no longer have and old school DeArvesol type meter movement VOM
( Simpson type ) so I was unable to get an accurate voltage reading from the brief pulses that the system provides.
Removing the actuator plate is simple .... one bolt and slide it sideways to clear the lock tabs from the metal recesses of the rear hatch lid. Look before you leap to determine the actual displacement direction. The actual actuator is now easy to remove with a torx screwdriver. You do not need to remove the pull cables to accomplish this.
I opened the actuator to see if I could determine why it failed. There is a tiny motor with a worm drive acting on a circular gear that tabs a flip mechanism to either the open or locked position.
Next time you need to redo this job you can ignore the cable pulling and simply slide over the black fork tab and the actuator will engage the outer latch handle so the deck will open freely.
During my autopsy, everything in the actuator seemed to work but the motor seems to have lost the gusto required to activate this flip mechanism despite ample grease. No obvious mechanical issues. I assume the motor has lost some of the "multi" windings common of small DC motors.
Time to replace it and give the old one the deep six.
I hope this helps someone faced with this annoying task. Good luck!

 

Great post. I have an 06 (85K) as well. I just encountered today my rear hatch lock not operating. I always turn to a forum first when I encounter a vehicle issue because I know someone has likely already experienced the same issue. I will start with the fuse as you mentioned & work my way toward the motor as probably necessary.

 

Can you hear it trying to actuate, Dobey? My '08 makes a screeching noise so I know it will eventually fail, same noise the door locks made as they were failing. But if you're not hearing anything I would press on with your troubleshooting.

 

You may be right. I have never heard any noises. My door locks have never failed and are still operational. Checked the fuse; it is fine. May get a new motor anyway and try it; if it doesn't fix it, I can return the motor if expensive. If not the motor, I probably will take it to a dealer because I am not mechanically inclined well enough to figure this out. Thanks for the advice.