While installing my Fass DDRP I found a 3 wire weatherpack connector with a 3 wire weatherpack sealed cap on it. What is it for? I figured it is for a manual truck, NNS and reverse lights. My truck is an automatic.
Could be the ECM. Previous owner installed an on/off switch to control the alternator because the PCM was over charging it. Who knows how much damage was done before I got the truck. The light was missing and I replaced it and functioned normally for awhile. Installed an internally regulated alternator and charges fine now. AC measures. 07 volts at the alternator with all accessories on.