isx 15 check engine light

[nitram1222]

I own 2016 Peterbilt 579 with Cummins ISX15 (07/2015) Engine ESN 79861398.Engine odometer 489 568 miles. I got Check engine light ON about a month ago. My mechanic checked with Cummins Insite and told me it is code 1144 and 1145. Truck was running great empty or loaded, no issue .They replaced 5th and 6th injector and also they replaced Injector harness and fuel pressure relieve valve and also they rebuild my fuel pump. Maybe after 80 miles from mechanic shop check engine light was ON again and I finished my trip and returned and they checked again and it was same code 1144 this time .Truck is running great with engine light on or off,no difference .They preformed Injector test on Cummins Insite and all 6 injectors passed .Anyone can help me what is wrong with this ? Thanks