Complete loss of electrical power

Follow the smaller battery positive wire to the under-hood fuse box. Be sure that connection is clean and tight.

No. The Powertrain Control Module controls the engine, none of the interior functions or systems. The bad connection I described is by far the most common cause of everything going dead on every brand of vehicle starting in the mid '90s. 99 out of 100 problems are solved by tightening that nut.

This can also be caused by a loose or corroded battery cable clamp, but most of the time the symptoms are a little different. If tightening nut doesn't solve this, we'll need to do some testing with an inexpensive digital voltmeter. If necessary, I can help you with that.

Normally everything is dead or goes dead the instant you try to crank the engine.

I can walk you through the steps right here. Assuming everything is dead, to get you started, first turn on the head lights, even though they don't work, so current is trying to flow. That's what makes these tests valid. Place one voltmeter probe on each battery post, not on the cable clamps attached to them. You'll find 12.6 volts if the battery is good and fully-charged. Now move one probe from the negative post to a paint and rust-free point on the body. If you no longer have 12.6 volts, the bad connection is between the two points you had the probe on. Assuming you still have 12.6 volts, move the other probe from the positive post to the cable clamp, (1/4" away). Should still have 12.6 volts. Now move it to the next place along the smaller wire. That should be the connection on the fuse box.

Here's where it gets hard to describe but it's real easy to do. Place the probe on the terminal that's crimped onto the end of that wire: 12.6 volts. Now move it to that stud or the nut on it. If you find low or 0 volts there, that is the point of the bad connection. That is a real common source of trouble on all models.

If multiple circuits are working, figure out which systems are dead, then we may need to just pick one of the easiest ones to diagnose, and when we solve that, the rest of the systems should also work. I can put some diagrams together and post them to help.

I'm only here a few hours each day, so if you have to make a long trip to the truck, I'll try to cover as many steps as possible in each reply.

I'm here about this time every day. We'll figure out where to go next once you post some test results.