I’m stumped. My 2006 ram 2500 5.9L auto trans won’t shift into third gear when engine light comes on. Its not producing a code even though the light comes on. I clear it out with my scan tool and it shifts fine but it starts out in 2nd gear. I drive less than a mile and the light comes back on. When I shut the truck off and restart it, it again won’t shift to third unless I hot rod it down the street. I replaced the govenor, transducer, and speed sensor along with a fluid and filter change. Anybody ever experience this?

 

YES,, my batteries where the culprit got to low,, First gear sloppy shifting,, 2nd wouldn't shift into 3rd etc. Check engine light was on,,, soon as i charged them up, no issues. Check your batteries, and ground. Make sure no corrosion etc.. TRACE all the wires.
If you got an update, let us know, hope things worked out.