Stuck in 4th gear

[Wadecool]

I have a 2022 6.7 with the 68RFE. Truck runs cross country towing 12k cargo trailer with 215,000 miles. In the past month, when I’m downshifting using the exhaust brake to slow down, it will jump to 4th gear and stay there. I’ll pull over, shut the truck off, restart and take off again and it’s back to normal. Sometimes this happens once a week, sometimes twice a day.

What’s going on here?

 

[Wadecool]

Pulled codes today and got P0868 and P0871

 

[steevesrivers]

New here, but that’s limp mode. Check ATF level, and replace fluid and filters if you don’t know when it was last done. But first, check atf level and condition. Level ground and in neutral or park. But that’s definitely limp mode.

 

[Daw14]

Check fluid level in neutral. Definitely due for filters and fluid change if nor done recently.