I bought my truck used with 80,000 miles on it and the "yellow" engine light stayed on more than it was off for around 5,000 miles. I read the manuel and it said 1 of 4 things can cause this:
run out of fuel
water in electrical system
I forgot the 4th reason
I always assumed it was bad fuel. The light would stay on for a few days (BTW, the truck ran fine) until I filled up somewhere else. It got to where I didnt even pay the light any attention. After about 5k, I deleted the DPF/cats and plugged in the SCT tuner. I have yet to see the light again. I have had it deleted for over 3k miles now. Now I am thinking that I had a clogged up/malfunctioning DPF.
Your truck has alot less miles then mine but who knows?? Could be the DPF??
Good luck man!!!