Underneath the trunk lid
Look on the trunk lid support arm.
Check inside the trunk, on the lid arm.
pick it or call a locksmith
There should be a sticker on the underside of the trunk lid - that's where it was on my 92 grand marquis
You will find a sticker in the trunck with the factory code printed on it.
You cannot reprogram it. A dealer can get you the Master Code if you've lost it.
Mine was under the trunk lid. When you open the trunk you can see it up underneath towards the back. A white sticker with 5 black numbers on it. '94 Grand Marquis
Enter the five digit factory-programmed code into the keypad. Press the 1-2 button immediately after the factory code has been entered, this must be pressed within five seconds. Enter your preferred five-digit personal code.
Usually on one of the Trunk Lift Rods. If you can't find it, a dealer can look up the Master Code for you.
A/C on/Defrost on during KOEO (Key On Engine Off) test.
The dealer should have that information. Also it may be in the owners manual. If you don't have one, try MOTORLIT.COM
The default location is on the Trunk Riser inside of the trunk on the left or right side. Look for a sticker.