Hi. In the back of your manual there should be a plastic card with the factory unlock code on it. If you have this, it's easy.
Programming Your Own Personal '''Entry Code
1. Enter the factory-set code ('''keypad will illuminate when first digit is pressed).
2. Press the 1/2 control within five seconds of step 1.
3. Enter your personal 5-digit code. Enter each digit within five seconds of the previous one.
Your personal code does '''not replace the factory-set code. You can use either code to unlock your vehicle. Each time you set a new personal code the module will erase the previous one in favor of the new code. The factory-set code can '''not be erased.
Erasing Your Personal Code or A Prior Owner's Code
1. Enter the factory-set code.
2. Press the 1/2 control within five seconds of step one 1.
3. Press the 7/8 and 9/0 controls at the same time within five seconds of step two.
The system will now only respond to the factory-set code.
Unlocking the Doors
1. Enter either the factory-set code or the personal code (Each digit must be pressed within five seconds of the prior digit). The interior lights will illuminate as soon as the first valid digit is pressed.
2. To unlock all the doors, enter the factory set code or a personal code and press the 3/4 control within five seconds of the drivers door unlocking.
Locking the Doors
1. Press 7/8 and 9/0 controls at the same time. The 5-digit code does '''not have to be entered to lock the doors.
Deactivating/Activating Auto-lock
1. Enter the five 5-digit code.
2. Press and hold 7/8 control.
3. Press and release 3/4 control while holding 7/8 control.
4. Release 7/8 control.
The horn will chirp once if auto-lock was deactivated or twice if auto-lock was activated.
Reference: http://townhall-talk.edmunds.com/direct/view/.f0fe9e4/14#MSG14
Also confirmed with the manual on my mom's Grand Marquis.'''''''''''''''
You cannot reprogram it. A dealer can get you the Master Code if you've lost it.
thats my question to you
You cannot change the master code. You can add a personal code by following the directions in the owner's manual but you will need the Master Code to do so. It's usually on a sticker on one of the Trunk Life Rods. If it's not there, a dealer can retrieve it for you.
To reset the keyless entry system on a 1997 Mercury Grand Marquis, start by disconnecting the vehicle's battery for about 10 minutes. Then, reconnect the battery and enter the vehicle. Press the "1" and "2" keys on the keypad simultaneously, which should reset the system. After this, you can program new codes if desired.
Ou812
Underneath the trunk lid
If the keyless entry code sticker is not located in the trunk of a 2002 Grand Marquis, it may be found on the owner's manual, in the glove compartment, or on the back of the keypad itself. Additionally, the code can sometimes be retrieved by a Ford dealership or a locksmith with the proper tools and access to the vehicle's electronic systems. If these options are not available, consider checking for any hidden locations in the vehicle.
Look on the trunk lid support arm.
Check inside the trunk, on the lid arm.
look on the trunk hinge there should be a sticker with the code on it
Usually on one of the Trunk Lift Rods.
There should be a sticker on the underside of the trunk lid - that's where it was on my 92 grand marquis