When I bought my D2 (With HK audio) the head unit was toast so I replaced it with a cheapo from Crutchfield, I then shortly after replaced the cargo door sub drivers because the ones in there has disintegrated to nothing. Anyway I liked the sound I was getting but was getting nothing from the rear doors, the fronts were working as was the sub. It didn't both me because 99% of the time it's just me in the truck anyway so only fronts was just fine. Well today I found out that the line outs in my head unit were only putting out signal to the front wires because the unit defaults to "subwoofer on" which I thought I wanted because, well, the vehicle has a subwoofer. Turns out that "sub on" turns off the rear line outs and replaces it with a subwoofer signal, which the vehicle doesn't need because the subwoofer frequency cutoffs are all taken care of in the HK amp. One quick switch in the settings menu from "sub off" to "sub on" and the whole truck fills with sound as the rear line outs come on!