Hmm, something sounds amiss here. The mileage display uses the CAN bus (a kind of network bus that lets the cars computers talk to each other).
I would guess that the iPod2Car system is using the CAN (or ACP) bus if it is messing with the mileage system. The bus also connects to other systems in the car so this could cause problems with other things if it does not communicate to the CAN bus correctly. The most probable thing is the installer disconnected the jack from the back of the radio and plugged in the iPod2Car alone so that the NAV system is no longer getting messages from the rest of the FEH modules. If this is true your GPS navigation system may also have problems because it will not get the "dead recon" and speed info from the car (this is used to minimize the GPS error). I think they are on the same connector as the CAN bus. You may be able to test this by attempting to enter a destination while moving (go into the address screen while parked and just leave that screen on while you are moving so you are not distracted by trying to enter that screen while driving). Normally you would get a "Option not available while driving" message. If you don't get this message your speed sensor is disconnected.
In any event it sounds like the iPod2Car system does not fully support the FEH NAV radio. if you look at the makers web site the FEH is not listed on the supported applications list. The Escape 2001-2004 is listed but there are significant differences in the FEH NAV audio system and the others.
Application guide for iPod2Car:
http://peripheralelectronics.com/pdf...%203-17-05.pdf