Turning the trunk lock counter-clockwise so the slot is horizontal when the key is removed will disable the cabin release lever. You can only do this with the master key. If you have the valet key you will not be able to open the trunk if the lock has been turned counter-clockwise.
A new key can be made/ordered if you have the lock code, which is underneath the passenger side door panel on the lock cylinder.
If your key refuses to open the trunk:
- Try pressing the key to the right side of the keyslot when it's in the horizontal completely locked position and then turn the key clockwise.
- Try the cabin trunk release lever on the drivers side floor door sill, next to the fuel cap release.
- Try sitting on the trunk, and then turn the key (MR2OC).
- WD40 may work, but this is not a good long-term solution as oil in locks tends to attract dust and gum up the tumbler mechanism.
- Get a new copy of the existing key. Often a key with fresh sharp edges is enough to do the trick.
- If you're up to it try you could drill a 1/4" hole at the top of the license plate. The hole will be behind and level with the top of the license plate, centered exactly under the lid. The lock latch is above and to the right of the hole. Use a thin screwdriver to open the latch with a clockwise quarter circle motion. (Red20V@MR2OC)
- If all else fails you can drill out the old lock with a 1/4" drill, and then replace with one from a parts car.
Illustrated Drill Method
BigMike posted step-by-step pictures of the 1/4" drill hole method to replies 16 & 17 here: http://www.mr2oc.com/showthread.php?p=5125314#post5125314
Step 1: If you drill at the top center of your license plate line, you'll screwdriver will likely hit the latch just to the left of where you need to be. Looking at the above picture you can see how the screwdriver is slightly slanted to the right. Therefore, BigMike advises to drill half an inch to the right of center. If you drill at center, then the screwdriver will make it's first contact as shown below in figure 1. It is possible be be stuck in this location not knowing where the screwdriver should go.
Step 2: Wiggle the screwdriver around and around until it falls in between both latches.
Step 3: Rotate the blade of the screwdriver 90-degrees to spread the latch apart.
Step 4: Once the latch has been spread apart, lean the screwdriver blade up the groove and pull the screwdriver out. Once the screwdriver is removed the latch will snap apart.
It is possible to get stuck between steps 3 and 4, having probably unlocked and relocked the latch unknowingly. It is therefore recommended to be patient, take your time, and check if the truck is unlocked frequently by gently pulling up on the truck. It is advised to pull up on the metal trunk lid itself rather than the fiberglass spoiler to prevent stressing the spoiler.