Commanded fuel pressure stuck

[windowrattler]

Have a ISX 2250 that I'm having a weird issue with. If you monitor fuel rail pressure commanded and actual it will get "stuck". I do have video but it's shakey. I'll try and describe it as best as possible.

The commanded FRP will all of sudden just stop changing. Tends to get stuck at three different numbers. 650 bar, 1056 bar and 1475 bar and will randomly change between the three values. When this happens the rail pressure tends to stay right around 900 bar +\- a little bit no matter where the commanded is "stuck" at and no matter the driving condition.

When this event happens with the oem cal it doesn't pop a check engine light. With a modded cal it trips a CEL sometimes for rail pressure. When it's doing this it can last a minute or two. It's not just a second or two thing.

I lean away from a physical problem like the fuel pump actuator because once commanded fp starts acting like it should everything is fine and it builds rail pressure like it should. I know the engine terminating resistor by the aft treat might not be hooked up but I don't think a datalink problem would present itself this way. So that kind of leads me to ECM being flakey. My other thought is its some type of protect mode or default mode. Thoughts?