I had the same problem... I had to replace the battery in my remote at the dealer... hope this helps
Its located on the passenger side before the rear axle in the middle of the rear doors
If I understand your question correctly, your vehicle may have a separate relay for each function. The relay for locking the doors by using the switch has gone bad.
By using the proper code - like 12321 or whatever your code is. You put the code in and then press 1-2 to open doors 3-4 to open back doors and 5-6 to open the trunk. When exiting you press 7-8 and 9-0 together to lock everything.
5x7 / 6x8 in the doors and 6x9 in the rear deck. See more info at the links below... http://www.autoclinix.com/Mercury/Front%20Speakers.html http://www.autoclinix.com/Mercury/Rear%20Speakers.html
If you can not unlock them with a key, you will have to call a locksmith.
There could be many reasons why the 1993 Grand Marquis make noises when the doors lock. The wiring could be off, or the motor could be going out.
Have you replaced the battery in the fob?
5x7 in the front doors; 6x9 in the rear deck (or 5 1/2" mounted in 6x9 adapters). See detailed info here... http://www.autoclinix.com/Mercury/Rear%20Speakers.html
Yes, IMMEDIATELY within 3 seconds after punching in your code, hit the 5 on your pad and your trunk will pop open. also if you immediately hit the 4 the other three doors will unlock.
If the key will not work in the door or the liftgate, you will need to call a locksmith or break a window.
On my 1995 Mercury Grand Marquis, you must have all the transmitters intended for use on your vehicle. Prior programing is erased and ALL must be done at the same time. 1) Enter the factory keyless entry code., 2) Press the 1/2 button on the keyless entry pad. 3) Press one button on each of the transmitters to be programmed. Each transmitter button must be pressed within seven seconds of the prior one. Each time a transmitter is successfully programmed, all of the vehicle doors will lock and then unlock to verify programming. If they did not lock/unlock, your transmitter was not programmed.