Hello everyone. I finally figured out how to get the back hatch open even while the electronic locks (both on the drivers door and key fob) failed to unlock the hatch. And you can forget taking the hatch paneling off until the door is open, since the two main screws holding the panel on are only accessible with the door open.......etc...etc..
After searching the internet, the above post and instructions by Stichypoo were the most comprehensive ( if not the only) ones available to address the problem of the liftgate that won't open with the electronic keyless entry type key.
I've just had the same problem with my 2007 Caliber SXT CRD (2.0L Turbodiesel) and, thanks to Stichypoo, solved the problem but with a variance and decided to join this forum specifically to post my experience here for other members' benefit.
I removed the 5 screws on the boombox hinge and then carefully, one at a time, cut off the 4 speaker wires to the boombox and taped off the ends just in case it should touch any metal bodywork, just to be safe. I needed to get the speakers out the way for ease of access.
The small hole in the back panel was too small and finicky for my liking so I proceeded to remove the panel even though the instructions said not to bother because it won't come off. The plastic panel is in 2 sections. One is the recessed section for the speakers and the other is the surround trim to the liftgate.There are 4 screws in the recessed section where the boombox goes and I took those out. Then I unclipped all the clips that hold the plastic panels to the bodywork including the large panel that surrounds the liftgate. This panel was still attached to the liftgate at the bottom but the top half where the window wiper goes was able to be pulled away far enough from the bodywork to enable the speakers' panel to be extracted. This gave me a huge opening with unrestrained access to the lock actuator.
The next problem was that the "white plastic knob" that Stichypoo talks about is in fact a lever of some sort and not a knob. This lever was stuck and wouldn't move down at all. I then proceeded to remove the 3 small "Torx" type screws that holds the body of the actuator together. Don't be scared to undo the screws. Everything in the actuator is straight forward, well secured, and nothing will fall apart when you open it. The actuator was now in 2 parts even though one section was still firmly attached to the liftgate. There is another smaller, Torx screw to be removed inside the half of the actuator that has just been removed. Once opened, this half contained a small DC motor with a wormgear and a round plastic gear. I could see the problem immediately. 2 teeth had broken off from the plastic gear and was jamming the wormgear and preventing it from turning and also prevented the white plastic lever from being manually operated.
Once I had removed the 2 broken bits of plastic that was stuck between the gears, everything freed up. I put the 2 halves of the actuator back together and tried the white plastic lever. It worked just fine and was able to be depressed about 1/2" and I was able to open the liftgate as per the instructions. The actuator worked fine after that but I will have to replace the unit as I'm afraid that more teeth will break off the plastic gear in future.
I have attached a close-up pic of the actuator for clarity as to the location of the cable release mechanism, white plastic lever and location of the Torx screws. Unfortunately I only decided to take a picture after everything was assembled so there's no pic of the inside showing the wormgear and the plastic gear.
I hope this helps someone else. Thanks to member Stichypoo for pointing me in the right direction.