My trunk lid will not open. I believe the key lock is frozen. I've used several lubricants to try to free it, but to no avail. There is no sound at all when using the fob release or the trunk release inside the passenger compartment. Perhaps I have a blown fuse. What fuse controls the electric trunk release.

Does Lumina sedan have rear seat pass thru to trunk ?? if sedan then a pull tab will be in seat upholstery near shelf / by rear window . pull it crawl in with Light Plus friend on outside to hand tools .. IF VAN must remove interior panels to gain access .. Try small thin needle nose pliers to pick broken KEY Piece out of lock 1 ST . if successful spray in Lubricant before trying another key . BUT must be reason lock jammed -- Frozen by weather change or Mechanism Disconnected due to lack of lubrication or worse Plastic Parts used in assembly by Factory .. DRILLING Lock Out will get it Open but new / used parts to repair are now on your shopping list ..

you might try lubricating the trunk latch with a silicone spray or wd-40 and unlocking it with the key while it is open. There is a chance there is a small broken spring in the latch that is not pulling it over to full unlock position and when you tried to shut the trunk it is actually already in the locked position.

remove the back seat. and try it from inside

Can you hear the lock click? You might need another person to listen while you activate the unlock mechanism. Can it be opened by a key? If so, try that. If it doesn't open, give a little push-down-and-release on the trunk lid while the key is in the unlock position.

If the lock makes no sound upon actuating an electric or lever-and-cable trunk-lid release, the problem is not user serviceable for the average car owner.

I could probably do the job, but I wouldn't, because it's too much work compared to the cost of an auto mechanic.

Lower the back seat and crawl into the trunk and see what the latch is doing when you activate the key fob. the trunk lid will have to be open to enable any repairs. Also an emergency release cable is probably visible (yellow handle) inside the trunk and will Open the trunk lid.

First, if it does need an actuator, you can save some money on labor getting it done at an idependent aftermarket shop rather than the dealer. Yes, the part will most likely have to come from the dealer, but let the shop deal with that. You do not have to pay dealership labor rates. It would pay to shop around.

Second, before any parts are purchaced, the actual CAUSE of the problem needs to be verified. Unfortunately, the ONLY way to do that is to get the trunk lid open and inspect the trunk lid latch components. If none of the three methods provided by the manufacturer for opening the trunk in a normal fashion will work, the trunk will have to be accessed by removing the back seat. Once the back seat is removed, a technician can reach into the trunk and remove the bolts that secure the trunk latch to get the trunk open. The latch parts can then be accessed to disassemble, inspect, and repair accordingly.

Please note that this is the ONLY way to do this without causing further damage to the vehicle. DO NOT allow anyone to attempt getting into the trunk any other way! (Do not use pry bars or screwdrivers on the trunk lid, key tumblers, etc..)

There are 3 phases to fixing your car's trunk lid release problem.

Phase 1: First check the fuse - once you know that's OK, then proceed to phase 2 (below).
The fuse for the trunk lock is
the bcm (pwr) 15A fuse in the instrument panel fuse box (behind panel at drivers right foot)

Check that fuse, as it is the power supply for the button on the dash that sends power to the actuator in the trunk.

Phase 2: Get the trunk open (without taking it to the dealership).
If you have remote keyless entry to the trunk, you could try that - but with the actuator
dead/dying, it shouldn't work.

Here are a couple of ideas to try to enter trunk while (a) actuator isn't working, and (b) all
valet lockout features (designed to deny valets access to the trunk) are in the "Lock" position:

There is the lock cylinder, which you stated is not functioning - put the key in, and it doesn't
turn. Just to be sure, consider: lubricate key with Graphite lock-type lubricant, and retry.

The trunk has 2 valet safetys...the locking rear seats which require access to the trunk to unlock, and then there is a valet switch in the trunk that locks the button on the dash from working to keep valet parking attendants out of the trunk. That may be in the lock position.

You can try accessing the center area of the fold down rear seat and see if you can unhinge the rear seat from there. Maybe reach in with your hand, or an extension-type tool.

there may be a way to fold the hinge away from the seat back so it can be removed from the hinge and give you access to the safety latch in the trunk and open it that way (white handle in trunk).
The white-handled safety latch release is desiged to prevent accidentally trapping children, and
if you can pull it with your extending-type or grasping-type tool, the trunk will open whether or
not the actuator motor is working.

Phase 3: Replace the Problem part.

Your failed part may be either (1) Trunk Release Relay, or (2) Trunk Lock Release Switch

My Satrun ION manual doesn't cover either of these parts, and the online parts houses, e.g.
http://www.rockauto.com/catalog/x,carcode,1431624,pgname,Electrical-Switch%2B%2526%252338%253B%2BRelay,a,search.yahoo.com%2BSearch%2Bfor%2B2004%2BSATURN
fail to provide instructions. One of those times a mechanic has to t=rely on his/her native
handiness and/or experience.
To identify which of these parts is bad, locae the Trunk Release Relay (call your dealer parts
dept. for helpful tips on finding it), then operate the dashboard trunk release button with your
ear close tothe relay - if it makes a noise, the problem is the Trunk Lock Release Switch in
the trunk lid, otherwise its the relay.

It sounds like the latch is stuck, if you crawl into the trunk through the fold down, is there an emergency release lever? If it has one and you can get the trunk open, make sure you lubricate all the moving parts on the latch before closing it again. You might also want to open and close it a few times to get the lubricant worked into it. I would use a heavy oil but you can probably get away with WD-40.

Try spraying the inner portion of it with some WD40 or similar lubricant. It sounds like something must be stuck. After you spray it, keep working the key and pushing the remote until you get some results. Good luck. Let me know how you make out.

It could probably use some penetrating lubricant once opened; don't use WD-40 as its properties are great for penetrating but not for long. There are a number of products, most available at auto parts stores or the chain hardware stores that have more durable lubricating properties.
Now, place one hand firmly on the trunk and 'bounce' the trunk lid while you try turning the key. It may take a few minutes until you hit it just right but I have never failed to open a stubborn trunk or hatch this way.
If it still doesn't open, you may have been lightly hit in the rear of the car (in a parking lot for example) that has minutely distorted the sheet metal where the stationary latch is mounted. In this case, you may have to hammer (with the side of your fist) the area below the lip of the trunk while trying to turn the key.