2000 Mercury Grand Marquis Transponder Key Question
 

Have a question about my 2000 Grand Marquis. First of all I have owned the car new since 2000. Better then 10 years ago I purchased 2 no name transponder keys,had them cut and programmed them myself. They worked all these years just like the originals. I now had 4 keys for the car. 2 Ford/Mercury factory keys and 2 no name keys. Most recently my wife lost one of our keys. Being I still had 3 working keys I wanted to buy another 2 no name brand and program them like I have done years back. I put each working key in the ignition to the on position and waited a few seconds just like I have done in the past listed in the Owners Manual and then I put the 2 new transponder keys in and did the same. The 3 I already had start the car no problem but neither of the 2 new keys will start the car. I went through the procedure four times. I always read that you needed 2 working keys to program any others. I had 3 working keys. 1 original Mercury Key and 2 non branded keys all working. Just wondering if the problem is that I needed to have 2 working Mercury factory keys. If so I can't understand why that would be being I have 3 working transponder keys. Can anyone shed any light on this?

Going to kind of answer my own question. Went out and purchased a transponder key locally and had them cut it. Brought that transponder key home and went through the process of programming it and it worked fine bringing me back up to 4 keys I now have for my car again. Guess the chips must be bad in the other 2 no name transponder keys. Don't know what else it could be other then that. Who knows there may not be any chips installed inside the keys. Wouldn't surprise me a bit with some of the knockoff stuff coming into the country.

Glad you got your problem solved.
I've found that the Genuine Mercury parts are your best bet. They may cost a bit more, but are well worth it in the long run.
I'm still using the original two (2) transponder keys for my '95 Grand Marquis restoration that has now clocked over 150,000 miles.