Check engine light flashes for 20-30 seconds on startup

[Golfnut]

I have a 2014 T6 80 with an ISX 15 that has been put on a diet by a member of this forum. it has given me absolutely zero issues but starting this week, the check engine light with a wrench in the middle of it flashes for about 20 to 30 seconds every time I start the truck. It has never done this before I had the oil changed on it a month ago along with fuel filters and I do not recall the issue starting immediately after that this is a farm truck that does not see a lot of miles that sees a lot of hours and it is harvest season coolant level is fine. The truck does not get over 180 or 185 degrees. Thoughts?