So I had posted on another thread with a similar problem, but wanted to start my own to begin at the beginning.
The vehicle is a 1996 Cherokee with the 4.0 inline 6

One day while driving home from work, it stopped running, like someone flipped a switch.

After I got it off the road, I attempted a restart, and it cranked fine but didn't fire, so I had it towed to shop.

Shop diagnosed a bad ignition coil, and the coil was replaced, I took the vehicle home. Later, I went to go grocery shopping, and the same shutdown occurred, had it towed back to shop.

This time they determined that the 30amp ASD fuse #20 was the culprit, and it would be fine from a cold start, but after the engine had been running a while, and come up to full operating temp, the fuse would blow again.

They ran further diagnostics, and then said that when the shutdown occurred the rear O2 sensor drew excessive current and that was the cause. I declined to have them replace the sensor since I could do that myself, and I unplugged the sensor figuring that would solve the issue.
Wrong. It shut down on me again, but since I was prepared with extra fuses I could limp it home.

When I got home I had a thought, if I disconnected the O2 sensor I ought to have a check engine light, and I didn't. I thought that was odd. So I figured I'd see if there were any codes stored. Code reader wouldn't connect, checked it on my wife's car it worked fine. So I don't know what is going on there.

So given that I didn't know exactly what the cause was, I decided to start chasing it.
Checked grounds for excess resistance, all were well under 5 ohms.
Unplugged the O2 sensor wiring from the harness in the engine bay, figuring that would eliminate any possibility that a short was occurring where the wires pass under the vehicle, and since that circuit was the one implicated I'd check that first.
Started it up it shut down after about 10minutes once it got hot.
I checked all the fuses in the fuse box in the engine compartment and inside the cab, all were good.

However I did notice this one little can under the dash was pretty damn hot. I'm not sure what it is can I get some help identifying it?

Little round silver can on the wiring.

 

A lot of OBD2 readers are not compatible with '96...I bought one that specifically said it was, cant remember the name, only $30

Pulling the rear O2 sensor will not throw a CEL light on a '96, but will generate and store a P0138 code

You may have a faulty wire or connection, the wires on these Jeeps are not very good quality

 

Still trying to get this tracked down.
looks like there may be a short in the wiring to the rear O2 sensor. Got a probe in the green/orange wire, at the PTC get a path to ground when that part of the harness is plugged in, which should not be. So I'll have to dig that part of the harness out I think.

 

Ever figure out the problem same thing here in my 96 but it won’t crank over mine seems to be fuel injector connectors