what year?? the 88-94's were nearly identical to the conti. In which case, the controller is probably mounted in the trunk, on the back of the seat (you will have to remove the trunk liner). on the module you will find the preset (non-changable without a lot of work) factory code. it will be like this:
*XXXXX* where x is a digit from 1-0
without that code, you cannot program in a 2nd code. in order to change the factory code, you need to disassemble the controller, and mess around inside it.
if its a later year, I cant help much.
ps.. just disconnecting the battery will erase the 2nd code, and reset the system to default mode of operation