location of navigation wires

PCM = Powertrain Control Module

It is the "brain" of your car. Just about every car since the early 90s (some in the 80s even) is now equipped with at least one... In regards to the "Passenger's Floor Mat" portion, I am assuming that you are working on a german car of some sort, say, Mercedes? They usually put their PCM under the passenger footwell area.

1M is probably referring to a specific pin/wire on the module, but since you did not provide exact information on what your vehicle is or why you are referring to it, this part is just a guess.