So, I think I found a solution to this. I'm an independent mechanical engineer, and I am currently consulting for a company that makes off-road gear. I just finished designing a tailgate storage system for a 100 series, and I was able to...
For those of you with the same problem on a 2003, here is some helpful info: your mirror ECU receives 12v switched through the ACC 7.5A fuse on the drivers side footwell, and 12V constant through the ECU-B2 fuse in the box in the passenger...
Just did this on my 2003 as well exactly as Ayune describes for the "later year" trucks. The following post about replacing the junction box does a great job showing how to get to these connectors. Pro tip be smarter than me and use a...