I got my wife a 99 ford expedition with the mach system and only the front passenger speaker is working. The hu has been replaced by a pioneer deh-p3000ib(which has a terrible interface). I pulled the driver side door panel off and the head unit out. I used my multimeter and do not have any between the head unit connector and the door. I traced things down and under dash there is a box with 2 connectors going into it, the speaker wires run into the box. It says something on it about keyless, anti theft, it was hard to read. I think it may be an amplifier for the door speakers, any one know? I can't find a wiring diagram online or much info about it, any info would be much appreciated.
