WARNING: This modification requires the removal, disassembly, modification, reassembly, and reinstallation of the trunk mounted lock cylinder. If you are not entirely confident in your ability to do this you should not attempt it. If performed improperly, you could damage the lock enough to make it unuseable, requiring you to purchase a new lock cylinder.
To perform this modification you will need several things:
STEP 1: REMOVE LOCK CYLINDER FROM CAR
When you remove the inside trunk panel the back of the lock is exposed. Twist the plastic clip downwards that holds the connecting rod, then pull the rod from the lever arm. Now remove the E-clip (using pliers and/or sharp screwdriver) holding the lever arm and spacers, then remove the arm and spacers and set them aside. Be sure to remember the order they were in! Two bolts hold the lock in place, remove them with a 10mm socket. The lock should now be free. The easiest way to remove the cylinder is to first remove the tag light assembly closest to the lock cylinder. From inside the trunk remove the three 10mm nuts holding the tag light assembly in place. Pull the tag light straight back into the trunk. You should now be able to reach through the hole left where the tag light was to help pull the lock cylinder out.
STEP 2: DISASSEMBLE LOCK CYLINDER
Now that the cylinder is free, you have to disassemble it. Be very careful or you will lose the small parts of the lock. Remove the polished cap (where the key goes in) using a small(narrow) screwdriver. Pry under the edge of the cap where the three indentations are to free the cap. The cap will bend somewhat but you should be able to get it off with out much distortion. The cap can be easily straightened with needle-nosed pliers once it is removed. The key door parts will be under the cap, remove the cap carefully so you won't lose the parts, set the cap and door parts aside. Now insert the key into the lock tumbler(the center part). Look in the back end of the lock (not the key end) and notice the brass retaining tab. Use a small screwdriver to press the brass tab down, while sliding the tumbler assembly out. Be sure to hold the key in the tumbler, and slowly remove the tumbler from the outer casing. IF THE KEY COMES OUT, YOUR LOCK WILL COME APART!!! When you slide the tumbler out the brass tab will try to come out since it is spring loaded. Carefully remove the brass tab and miniature spring and aside to prevent loss. Set aside the outer lock casing.
STEP 3: GRIND OFF METAL TAB PREVENTING ROTATION
Once again I must stress: DO NOT ALLOW THE KEY TO COME OUT! Clean any excess grease off of the tumbler. Examine the tumbler and compare with the photos below to determine which tab needs to be removed. Use a Dremel or similar tool to grind off the raised tab shown in the photos. WEAR EYE PROTECTION WHILE GRINDING!
Do not carve too deeply with the Dremel. Be sure not to leave any rough edges, and clean all metal fragments off of the tumbler before re-inserting into the casing. Insert the tumbler with key still inside and verify that key now turns both directions smoothly. If it seems to be snagging when turning counter-clockwise remove tumbler/key and verify that all of the tab was removed. If the key turns smoothly you are ready to put it back together. NOTE: Older locks may be worn enough that the brass key "bumps" may stick slightly out of the tumbler, causing snagging while turning backwards. Use a grinding stone in Dremel to slightly round the edges of the "bumps" if necessary.
STEP 4: REASSEMBLE LOCK CYLINDER
Insert the tumbler COMPLETELY in the casing, and carefully remove the key leaving the tumbler in the casing. Place the key door parts back on top of the key opening in the correct position. The spring will try to push the key door up as you try to put the cap back on. To put the cap on, place a screwdriver through the center of the cap and hold the key door down with the tip of the screwdriver. Slide the cap down the screwdriver and onto the lock cylinder. Use pliers to press the sides of the cap down if necessary, ensuring the cap will stay on the cylinder. Now insert the key and test rotation one more time before reinstalling in car.
STEP 5: INSTALL LOCK CYLINDER INTO CAR
Reinstall lock cylinder in car, reversing removal steps. It will be difficult to get the cylinder back in place because the rear panel is so close to the car. Keep trying and you will get it eventually. Once cylinder is in place, replace 10mm bolts. Replace tag light assembly. Replace spacers and lever arm on lock shaft in correct order, and secure with E-clip. Place connecting rod back in hole on lock arm and rotate plastic clip until rod is locked in place. Replace trunk inner panel.
YOU ARE DONE!
To use the locking feature, the trunk lid must be closed. Verify the console release still works properly. Now close trunk lid, insert key, and turn key counter-clockwise. You should hear and feel a small "pop". This is the console release being disabled. Pull the console release, it should now do nothing. Place key in trunk lock and turn clockwise, opening trunk. You will propably hear two "pops", the first is the console release being reactivated, the second is the trunk latch opening. Close trunk lid and pull console release to verify it now opens trunk. THAT'S IT!
One alternative approach that disables the release and should reversible follows. This approach is quicker and easier than the procedure described above, but should be considered a one-time fix because it not allow you to switch the release on and off (unless you complete the steps to reverse the procedure). This mod can be done in about 5 minutes by someone with minimal mechanical abilities (if I can do it, you can, too).
Step One: In order to get to the hinge, you must pull off the cover/carpet. Remove the little round clips that cover the hinge mechanism in the lower inside part of your trunk. To remove each one, put your fingernails around the inner circle and pull it until it pops out slightly. Then pull the inner circle and the entire clip should come out easily. I removed the 4-6 clips surrounding the hinge mechanism.
Step Two: Put in your key and turn it. You will see that there are two wires/mechanisms that form the trunk latch. You will see that one is activated by turning your key. The other is activated by pulling the trunk release cable, which is activated by the trunk release lever inside the center console. That cable is the one you want to disconnect. It ends with a little ball (slightly bigger than a BB) that fits inside a bracket that is connected to the hinge mechanism.
Step Three: The ball does not come out of the bracket, so you can simply bend (I used pliers) one little prong of the bracket (it has two prongs) a little bit. You should bend it just enough to allow you to pull out the ball. Now your internal release has been rendered ineffective.
CAUTION: I assume that you can reactivate this release at any time by putting the ball back in the bracket and bending the prong back into place. I haven't tried this, so I can't be positive that it won't break the prong or cause something else to go wrong. Caveat emptor!
Step Four: Make sure that your key
still turns the hinge and will open your trunk before you close it! Then attach
the clips to put the carpet/cover back into place. You have now made the trunk
much more secure!