Cummins N14 electrical problems

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Does your truck have the diagnostic switch on dash to check codes.
Sounds like you have a bad sensor that is affected the ecm from reading the rest.
I have a 99 fld120 that would give me numerous faults over the past few months. Finally the ecm derated motor and gave me red shut down warning.
One of the warnings was barametric air pressure sensor.
I changed that and life has been good for about a month. Knock on wood.
I've changed the air boost sensor a couple months ago also.
I'm not good diagnosing electrical problems so I change parts.
Still cheaper than paying a dealer shop.

Good luck.

 

You may have an issue in your dash. I chased a low oil pressure problem for weeks, turned out to be a loose wire on a circuit board in the dash.

Had the loose wire re-soldered and have not had any problems since.

My truck is also an '01 with an N14.

 

Maybe these guys can chime in, @boneebone, @KB3MMX & @Dave_in_AZ

 

I would check the all wiring from the ECM to battery to starter and ground wires.

I had a similar experience years after going through Louisiana.

My truck would hit a bump, lose power and than keep on running.

It wound out to be a chafed wire by the starter causing the truck to turn off in a split second, than turn back on.

 

Have you driven the truck since repair? Is the intermittent power loss gone?

 

As others said check all wiring very well but it's a very real possibility your ECM needs replaced. (Ignore mechanics that say it's fine unless they split the case and actually bench test all the circuitry)
The unstable 5v side is a common symptom of a failing ECM. You've already put a fresh harness on the engine.