intermittent power lost to ecm

while chasing down all possible causes of my electrical gremlin, i discovered some poor wiring practice by the individual who owned the truck before me. there is a switch on the dash that turns on lights located at the bottom of my cab and on the steps. i never use it and haven't looked into the way it was wired until today. i decided to disconnect all the lights and chase the wires powering them. i followed the main wire powering these lights into the cab.

it terminated at this junction which is the bottom whitish wire in the picture...



then on the other side is this yellow wire...



i loose the yellow wire in the dash...



so i move to the switch, upper left corner of the picture there is a tag that has optional written on it. looks like it would fit in the space above the switch...



this is the wiring the switch was plugged into. i tried to chase this wiring, but loose it in the dash too...



now i dont know if this has any bearing on my problem, but thought i would share anyways.

 

gotcha, thx

 

this is how my batteries are wired, the small white wires are the unswitched power to the ecm.



since an earlier post made mention of a bad wire connection at the alt. caused the turn signals to act up, i am posting these seemingly unrelated items to maybe help me identify a potential cause of my problem.

 

thought i would give an update of what i have done to cure my electrical gremlin(s)...

• found out that "weather proof" connectors are not so weather proof. the plug giving power to the ecm had loose connectors and were corroded. cleaned, tightened and resealed.
• there was a leak in the firewall letting water get to the fuse panel. used silicon to seal wiring at firewall.
• rewired chicken lights and tts lights, this alone fixed alot of electrical shorts.
• put in a new ignition switch
• changed out the fuel solenoid. turns out, who ever changed this out the last time put a part in backwards. which caused a fuel leak and silicon sealant was used to stop the leak. doing this gummed up the internal pieces that i believe was affecting the solenoid in some manner.

so far truck seems to be running fine...