Need help! Need the truck this week.

The truck is a 1999 FLD120 with a Cummins N-14 Celect+.
Brief history:
PARTS~
New injectors
New oil pump with cooler bypass
New Oil cooler
New main bearings
EMC rebuild (Last week)
New throttle pedal sensor
New Alternator
New batteries
And many other things not really related I don't think.
Excellent multi point grounds established on various points on truck frame and engine
Problems~
Injectors 1-6 codes & 5 Volt power supply fault
-ECM rebuild corrected these codes
Engine shuts down when throttle goes back to neutral.

Here is the situation:
-Got the ECM back this week and got it installed.
-Was told all codes were cleared with the rebuild so I didn't try to read the codes.
-100° outside. 65 mph test run with no trailer
-26 miles, the problem starts: Engine stops running when throttle is left off
-Can restart every time and keep going.
-Even without clutch usage, the engine stops running when throttle is let off of
-Cruise control works but if going down a grade, no throttle by cruise control will shut engine off
-Got to here I was going (66 miles), read codes and got SID 251~power supply, inactive, 41 times (not 5 volt power supply like previous code before ECM rebuild), and erased codes
-Cleared codes and drove home
-same scenario the 66 miles back home, Engine stopping while letting off the throttle
_Got home, read the codes and ZERO codes were present.

What should I check from here?
Throttle position sensor?
Is there an external power supply I'm not aware of?
What would be causing an engine stop if I let off the throttle?

Any help is greatly appreciated.

 

Is there an external power supply I'm not aware of for the ECM?

 

Just wondering if a additional power wire (switched of course) to the fuel solenoid would help correct this shut down situation? Or bypass a low voltage situation while running?

 

This issue has been the same for a year now, been from Utah to North Carolina with the truck and none of them can help me for less than $2000.

If you price all the parts I've put in so far, it's well over 8k.

I just seem to have a hard time paying $250 an hour for something that can probably be bypassed for $20

Not really helping with a repair option but thamks!

 

Who says I don't know what I'm doing?

Every part I've changed on this truck needed to be changed and I saved thousands of dollars by doing the work myself.
When I did the injectors, it was running on 3 cylinders. Oil pump? 18 psi of pressure at 1500 rpm. ECM? Injector timing board was throwing faults. Only part I just threw at it was the throttle sensor.

I just thought that since it was the end of the day, time to come in and have some dinner and relax, I would ask here to see if anyone had any insight before I start diagnosing and tearing into the truck.

The only thing that I bought and shouldn't have was the truck itself. haha

But, anyone have some informative comments to where I should start looking for this issue to get it corrected other than just find a shop that knows what they are doing?

The nearest Cummins dealer is 150 miles away and have never had much luck with them at all. I get the normal "Bring it in and we'll see what we can find", but I will say that when I'm travelling with the truck, Cummins dealerships are 1000% more helpful than Freightliner dealerships.

 

Shuts off like you turn the key off. Push the clutch in and she fires right back up

Weird thing is, it doesn't matter if the clutch is used or not while shifting. Let off the throttle and it dies like the key is shut off.

All my gauges read good and no engine codes.

It does have a non-OEM fuel solenoid on it but if that was failing, it doesn't make sense that would only happen during shifting and then start right back up.

If the motor was shutting down on a safety due to RPM change, it should be throwing a code but nothing is stored.

That's why I'm thinking a jumper to the solenoid would let me know whether its dropping the 12v power and shutting the fuel off.

If I don't shift or let my foot off the throttle, she'll pull like a train all day long