Couple notes. First off, great thread!
...Regarding the extra plug, it's coming out of the single M004 relay, not the M002. And yes, the 02 and 04 are connected via the OTHER plug coming out of the M004. If this doesn't make sense, I'll take a picture tonight. But basically my "H" relay has both a male double plug and a female double plug coming out of it. Weird or not?
Not weird at all. That is made so you could theoretically add a second M004 system that activated some driving lights or similar on high-beam function. If you look at the bottom of the relay base, the two plugs are 100% identical in function, just opposite ends so one will plug into the M004 per the instructions and the other would be used to piggy back and additional harness or simply not be used. It could easily be cut from the relay base with a couple snips too.
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Second question: I am assuming you do NOT rewire the ARB pickup socket--just the original source from the truck, correct?
The instructions for the M002 do specify you modify the wiring orientation
on the ARB M002's pickup harness lead not the vehicle itself, if you do so the wiring colors specified in the instructions will match up exactly. The instructions could certainly stand a refresh as you have to read it a few times to understand they are referring to the "pickup plug" which is the new harness not the original. Now, if you wire it per the way
@lechnito did so on his harness, the end results is the exact same as the same connections should be made, so no issue there.
Vehicle Harness -> M002 Harness (Function)
Red/Green - Red/Green (Ground from headlight switch, activates Low Beam)
Red/Yellow - Black (Ground from headlight switch, activates High Beam)
Red/White (Left Hand of vehicle) & Red/Blue (Right hand of vehicle) - Red (12V fused power from the battery)
Assuming all of these connections are made as such, the IPF M002/M004 should run a 4 headlight system as designed.