The rear hatch door won't open. Could the locking mechanism be jammed or would this be an electrical problem?. please help.

remove rear panel and check latch for damage or linkage disconnect --also check electrical connections to other components

Found this wiring diagram for lift gate, if that is what we're talking about? Not only check the fuses, check fuse circuit for voltage. Use a testlite.

latch and lock are jammed from the hit will probably need to pry hatch over or lift while unlocking to open than adjust hatch or latch for proper working order also check relay and fuse hit may have also damaged wiring

The lock assy

If, when closing the rear hatch, it hits "hard" just before it reaches the closed position; it is very likely that the latch mechanism in the hatch is "stuck" in the latched or closed position already. This is a fairly common occurrence and takes less than a few minutes to fix. Literally.

In order to allow the latch to close around the mating piece on the car body, it will need to be opened first. To open a closed latch mechanism, you will need to simulate opening the hatch from its normal closed position. With the hatch open, look at the latch mechanism. It will align with the bar on the opening of the car. Adjust the hatch / your view to see how the mechanism would be wrapped around the bar on the body - keeping the hatch securely shut. Once you see an opening in the mechanism described above, slip the shaft of a sturdy screwdriver into the opening. Apply a pulling pressure outward - away from the latch on the screwdriver with one hand, and with the other hand (or with the help of an assistant), operate the handle / lock of the hatch the way you did when the hatch was closed. Immediately upon operating the handle / lock, the latch mechanism will unlock, and the pulling pressure of the screwdriver simulates the hatch being pulled away from the bar on the car - and seemingly magically - open allowing the screwdriver to be pulled out.

Next, you'll need to determine and correct the cause of the latch being in the wrong position. It could be something as simple as someone pushing the mechanism shut when the hatch was open; or it may be caused by a poorly lubricated mechanism that is not snapping into a fully open position. When this happens, it is likely the the closing motion of the hatch actually snaps the mechanism shut when it is stuck on the leading edge of the latch - instead of in the "throat" of the latch (where the screwdriver was). A liberal amount of a dry lubricant such as silicone or graphite applied to the mechanism and "worked in" through repeated opening and closing motions of the hatch would be a good start. Resist the temptation of using a wet lubricant like oil, grease, WD-40, etc. as these attract dirt and dust - which can interfere with a nice, fluid movement of the these latching parts. If there is already a lot of dirt, dust or rust, build up on the latch mechanism, it should be cleaned as good as possible before applying lubricant. Use an electrical contact type cleaner as these clean, degrease, dry quickly and leave no residue.

If you are unable to to get the latch to work - have your mechanic or auto servicer look at it. They should be able to quickly diagnose and free the latch. Most will not even bother to charge you to do this - if this is the cause of the problem.

I hope this helps & good luck!

sounds like the system needs lubricated you'll have to remove door panel to access the rods as well as the lock mechanism clean off an lub check for any bent or loose parts rubbing

The locking mechanism on the rear lift gate for the Chevy Uplander has some plastic and rubber-coated parts that can get jammed. If you can pull back the panel from the inside top near the glass, you can reach down and try to spray some silicone lubricant into the lock. This could help get those parts unstuck so they spring back when you pull on the handle latch from the outside. Once you get the rear hatch open, I recommend taking out the locking mechanism and thoroughly lubricating it. Your rear lift gate will start to release very easily from then on.

Check the unlock mechanism for the hatch. These are controlled by an electrical motor pulling a cable. If the cable came loose you might or might not hear the click click that it makes. I would also check the fuses and relays related to the system. Usually if you can get the interior panel off all the innards are exposed. I would suggest pulling that panel off, then triggering the keyless remote and see if anything moves, that might pinpoint where it has gone bad.

After getting in earlier this morning and closing it while at the park, when we were done at the park, we went to open the rear hatch, and even though the electrical lock sounded normal, it would not release. Completely jammed.

The hatch is probably "jammed".
Has the hatch opened by itself while you are driving? That is a symptom....
Using a second person/helper, press the "open" button while you pull hard to pop it open.
If it opens, then the lock mechanism needs adjusting and tightening. There are two bolts that hold the catch hook. Once you adjust the catch, be sure to "open" the latch before you close the hatch. (rhyme not on purpose)...

Hope this helps!