I have a nice good running 1998 blazer that runs good for 30-50 minutes then the dash lights flicker and the entire truck turns off. After it shuts off it won’t even engage the starter. Last time it did this it made 4x4 permanently engaged so it couldn’t even roll easy (what a POS). When the electronics work everything works, even cruise control. Should I look at the PCM? I’ve already replaced the ignition switch wiring other than that I have no clue what to do other than junk the thing.

 

Have you checked the most obvious thing, the battery cables? Make sure they're clean and tight (at both ends).

 

yep they’re good and tight new battery too

 

Also check your grounds, bad grounds can cause problems that you wouldn't expect. Make sure that the contacts are clean and I apply a thin film of grease to them. I am not familiar with the Blazer but my pickup truck has several other places that the body is grounded to the frame.

 

Adding my 5c worth of experience with Blazers and in this forum.

Have a good look at the electrical wiring especially in the engine bay.
We have seen some crazy stuff over the years in any form of bad repairs, rat's nests of added wiring, bypasses and such which can cause all sorts of problems.
Also check all the fuses. Remove them and visually inspect and measure if possible. I have seen corroded fuses cutting out when they had heated up to a certain point. Check all the fuse boxes and relay boxes for molten connector sockets/pins.

Also if rodents had a go at your wiring this can cause all sort of intermittent issues.
It would be interesting to see what else might still work as it should once it shuts down.
Power windows, lights, turn signals, emergency flashers, wipers, ventilation, locks, even courtesy lights and lights in the sunshade mirrors. etc. All electrical stuff. This would narrow down the affected circuitry.