security door lock?

A freind of mine recently aquired a 91' linclon town car with the security door lock on the outside and I am wondering how one could reprogram the code? when he bought the car from the guy gave him the code that is inoperable and he would like to be able to use that code. is there maybe someway to manually reprogram them or something?

Yes you can !!

First you'll have to locate the Keyless Entry Control Module and crack it open. Simple to do.

Second, you'll see five resistors soldered to the main circuit board. These resistors can be soldered to the board in different circuit "holes", therefor, soldering them in different positions will change the code accordingly.

On another note, the previous owner may have programmed/memorized a "personal" user code that was erased when the battery was disconnected for a long time. A "personal" code can be programmed using the "permanent" code from the sticker on the right-side trunklid support arm. Also (and this is obvious by now) the permanent code can be "read" from the positions the resistors are soldered once the Control Module is opened.

bdklein wrote a fantastic tutorial on the whole process with pictures and graphics. I did get his permission reference his work.

Here's one of bdklein's graphics:
http://webpages.cwia.com/~bdklein/sho%20code.jpg


And here's bdklein's writeup:
http://webpages.cwia.com/~bdklein/sho.htm