2003 Volvo With N14 Celect Plus Having Problems

Having problems with my 2003 Volvo with Cummins N-14 engine and regular 10 speed tranny. Have the truck for 11years and know it pretty well. Engine would cut off after about 3-5 hours of driving. It started about 2 month ago , and seems to happen more often. After first time it happened I was able to drive for 3000 miles with no problems. Starts back in 5 to 40 min. Then shuts down in 10-25 miles again. Sometimes it would just drag for a part of a second but continues to run. Last time somehow I was able to find that driving slower would help to avoid problem so I was able to drive 240 miles on 55mph/90kmh and keeping RPM's around 1250-1300. So I was able to get back home.
Yesterday I drove for 25miles, kept it idle for 2.5 hours while getting loaded and after 10 miles on a way back to yard it cut off on me again right after EPS and engine harness replacement. So it seems that it is not necessary to drive al the time to bring the issue up.
So far I have replaced part of positive red ECM wire that goes from battery compartment together with fuse housing.
EPS- engine position sensor even if the old one showed good resistance on both reels.
Engine harness (goes into plugs A and C of ECM)
Plug of OEM harness that goes into ECM hole "B"
Ground cable between starter and engine block.
What I noticed is that Cummins Roadrelay 4 that I have in a dashboard shows constantly fluctuating RPM's like +20/-20 from average set. I don't feel it on engine noise while idle also not visible on tachometer's needle. It used to fluctuate all the time but only like +5/-5.
When the engine shuts down the onboard diagnostics would say "MID128 Engine controller not responding" Cummins Roadrelay would pop "Data link failure".
At the beginning of this nightmare it used to say "Engine power supply electrical fault".
When the engine comes back to communicating diagnostics would read:
SAE J 1708 data link electrical fault - just on a last occasion.
SID 251 Power supply voltage below normal - on some occasions.
Code 241 VSS Circuit becomes inactive when back to driving.
Also EPS circuit fault after every stop becomes inactive after back to drive
PID 190 EPS intermit or incorr on one occasion became inactive
After 2 drags when an engine shuts down for a part of a second but continues to drive code 343 "ECM failure service soon" showed up and was already inactive.
No problems on a dashboard cluster with lamps, gauges.
What else to look at ECM?, data link? Fuel supply? Timing gear? I would appreciate any thoughts of yours. Thank you!

 

Thank you for your reply. Yes that is the very first time with these issues. Did you see them going bad without red "Stop" light, without yellow "check engine" light, onboard troubleshooter would not say anything about engine controller nor Cummins Roadrellay4. I saw all these things on other truck with bad ECM. That one had code 111 "bad microprocessor" all the time. M&K Volvo kept the truck for 3 weeks and still the same results after $3K spent. "We waiting for a code don't want to throw parts at it". It shutdown only once during 30 hrs. of idle at 900rpm with no code. Came to them once drove it around for three hours - nothing happened. The truck was idling for more than 5hrs before I took it for a drive. So I pulled it out of M&K yesterday and when I had 300 yards till my parking lot she gave up on me after about 12 miles of driving and 7 hrs. of idling before that. With the same "MID128 Engine Not Responding". Came back in 5min.

 

Oh yes I did check. Have had issues with that one before.

 

The entire engine harness is new....

 

I did and spoke with Terry some time ago. Thank you.