I just inherited a 2001 Mercury Marquis from my dad (God rest his soul).
The only thing I have not figured out is the "keyless Entry System."

The user manual says the factory set code is on the owner's wallet card (can't find) or taped to the computer module or at the dealer.

Where the heck is the computer module? Hope I can find the code there.

Will it cost me to get the code from the dealer?

 

THe module that has the code on it should be inside the driver door.. Not terrible to get to, but it does invovle removing the door panel...

 

Sir, thank you. I removed the door panel and obtained the code. Everything is good now, except I was driving in a torrential down pour and hit a pretty big pool of water. coincidentally, I noticed the "Check Engine" light was on.
Do you think it went on because of a splash of water on the engine?

 

Glad you found it!!! I'll bet something just got wet and angered the computer.. If it runs okay I'd follow the advice in your other post..