Shop before you spend

It sounds like the lock actuator has failed or has a poor connection which won't allow the latch to release. What you will need to do is remove the inside rear hatch panel to access the lock actuator. Once you get to the latch use a flat screwdriver to release the latch being careful not to damage the glass.

----------- Click this link below for more troubleshooting:-- http://technoanswers.blogspot.com/2011/09/rear-hatch-wont-open-on-2005-gmc-yukon.html -------- This will help.Thanks.Helpmech.

there's a plastic actuator inside the tailgate that probably broke or at least came loose. You have to crawl into the back and release it. I ended up having to cut a little piece of carpet in the middle on the top of the tailgate area. Right where it fastens. You can manually release the glass with a screwdriver at that point. To replace the actuator, you need to take off the entire tailgate trim and metal underneath that to get to it. It sounds like a pain but trust me, not having the back glass be able to open or the tailgate area is much worse. It takes about 45 minutes to fix. The actuators are less than $10

I had the same trouble and found that I had to disconnect the glass hatch switch. It is probably defective like mine. I had to release the door by going from the inside and opening a little plastic door and open the whole hatch by using the emergency lever. Then I had to unscrew the plastic panel near the glass hatch and pry it apart just enough to disconnect the glass hatch switch. It is just a small connector that pulls apart. There are two connectors. One for the back wiper and then the glass hatch so make sure you disconnect the right one. This allows me to use the whole door but the glass hatch becomes useless unless you get a new switch.

Sometimes there is a safety sensor that does not allow it to open if the vehicle is in gear. This sensor may be faulty but most likely not the problem. Remove the inner panel on the back hatch and inspect the linkages from the outside handles to the releases inside the door for the glass and hatch. These have most likely came loose from the latches they operate

The glass hatch release handles fail all the time on these models (which is why the system was eliminated in 2009 models).

The glass hatch handle is $32 list from the dealer.

Removal and replacement requires a philips screwdriver and a 10mm socket and ratchet with extension.

Open the glass hatch by manually activating it through the access hole on the inside of the tailgate (small square panel covering it)

Remove the two philips screws and the one pop fastener holding the plastic trim on the back of the glass hatch handle area.

Remove the two 10mm nuts holding the handle on, unplug the wire and remove, noting the routing of the wiring on removal.

Reassemble in opposite order, being sure to route the wiring correctly.