Fuel pump relay?

Set it at 600 RPM- for the throttle position sensor voltage at closed throttle should be 1.25volts or less.

Turn the key to run and measure the voltage at the TPS and at the same time turn the TPS till you get 1.25volts or less. Unable to get the right reading-replace it

This problem sounds like it rears its' ugly head when the engine is warmed up -- clue?
If the TPS checks out OK, then check the ignition control module and the coolant temperature sensor. Just replacing these items is probably a good move -- considering you have 228000 miles on the truck.
The ground for the fuel pump commonly corrodes -- check it out also.

The computer energize the fuel pump relay then it goes to the fuse then to the fuel pump-

Sounds like the computer is not powering the coil side of the relay and also from the fusible link

There should not be voltage to the pump when the engine isn't running. In the event of a crash that ruptured a fuel line, that would allow raw fuel to be pumped onto the ground creating a fire hazard. Chrysler Engine Computers turn on the fuel pump relay or automatic shutdown relay when it sees engine rotation, (cranking or running) by the pulses from the crankshaft position sensor and the camshaft position sensor. If either of those sensors fail, you won't have spark either so it's important to check for fuel pressure AND spark, and not get stuck on the first thing you find missing. Newer GM vehicles use a similar system although I'm not as familiar with it as I am with the Chrysler products. On some older GMs, they used a tap on the oil pressure sending unit to turn on the fuel pump relay. In a crash, the engine would stall if the fuel line was broken. That means no oil pressure so the fuel pump would stop running. Both systems are very effective and relatively simple to diagnose, ... Most of the time. The main thing to remember is to do any diagnosis while a helper is cranking the engine, not just with the ignition switch turned on.

Did you test for power as I suggested on your last post>> check it at the fuel pump connector. It will only be there for 2 seconds with key on engine off.

No, the ecm cannot be bench tested after removal.

Roy

Suspect fuselink need engin size and trans type

Check fuselinks at battery junction box Gray 20 amp

The orange wire connects to afusiblelink whichis gray. It may be at the alternator or on the starter. The orange wire goes to the fuel pum relay as well as the oil pressure switch and back to ecm. But check the fusible link maybe only on ore two wires are connected.