I am posing this question for a friend of mine, who has a 2003
Expedition. His Expy was broken into last week, one of the stupid things stolen was his warranty folder. In it was the business size card with the code to his Keyless Door Entry system.

When he realized that it was in the folder, he changed the code.
BUT!!!! He tells me, that the old factory code still works also.
So now both codes work, the factory assigned, and his
newly made up code.

Is it possible to CLEAR the old code when installing a new code????

 

That is correct, you can only add an additional code, not eliminate the factory set code. Not sure if the dealer can or not, I guess its worth asking.

 

The dealer can change the module. The factory code is set using four resistors internal to the module.