2003 4.6l v8 Supercrew here.. 338,000 miles. Bought new launch scan tool and was excited to finally get to see in real time why or where my misfiring is from......What a rabbit hole its led me down man let me tell ya. Well, first ill keep it as simple as possible. After all kinds of guessing and reading and testing and probing yada yada yada im here- So my can bus is down. 4volts steady on pin 10 at the dlc and 0volts at pin 2 with key at run position. (Pic is last time the scanner was able to communicate partially. Wkuld read pcm. Now wont read cluster either fyi)

. No power on fuses 16 18 20 21 i believe as well 26 27 all of which are inside the cab under drivers side dash. no power from red and blue wire from ignition switch that is supposed to power said fuses(is that right?). Tried to use fused jumper from all run/start 12v feeds and truck cranks when key is turned to run position on its own. Scan tool wont communicate and I can not figure it out. Tore apart entire front end of truck almost including behind dash hunting shorted wires. Nothing. Tried switching pcm. Still nothing. When key is off pin 16 at the dlc shows 12 volts but when key is turned to run or start voltage drops to 10-11.6 volts sometimes 9. This all started trying to figure out a misfire and sluggish performance with no codes other than crank sensor code. P0135. But crank sensor tests good. Please for the love of God help me haha. Theres more info but ill leave it there for now I guess. Any ideas?

 

Delete the flippin' poll. Troubleshooting isn't a popularity contest.

Your truck does not have a CAN bus, too old.