No longer switches to eco mode

[Reverse]

2020 5.7, 154K miles

I realized a while ago that I had not seen the 'eco' light come on anymore. Over the last month, I have kept an eye on it, and have not seen it come on once, not even on roads where it previously would.
I checked for OBDII fault codes, and there are none. No lights on dash. I does seem to idle a little lumpy as well.

Any suggestions on what could cause this?

 

[SD Rebel]

First, double check to make sure the light wasn't switched off. Go back to settings and verify, you never know.

It not turning on could be the result of other issues, especially if it feels off at idle. I would take it to an independent shop that has the full factory level ODBII reader. They maybe able to shed more light there you will not be able to see with your reader.