The relay is in the underhood fuse block. Should be inexpensive at a parts store and take seconds to change. Those seem to be notorious for failing. Seems like that would cause the symptoms you described.
I believe "reductant" is the DEF fluid and your pump isn't functioning properly. Check your DEF spray nozzle, it could be clogged with urea deposits, causing the issue.
When I had issues with my DEF system (don't recall the code), I cleaned the nozzle and mount hole with steam*, cleared the...
If you have trouble with getting SFT to turn off your EGR, you could use a restrictor in the tube to significantly limit the flow. There are some plates on the internet, but I've been using a very inexpensive MacGuyver restrictor (SFT stage 1 w/ EGR on - have to pass emissions still): 1 Ace...
Given that the regens had a positive effect, I'm thinking that your DPF just needs more time with EGTs above about 750°F to burn more soot off. If you have mountains nearby to do a long, highway speed, drive up, or access to a big, aerodynamically impaired trailer to pull down the highway...
If I may add...
That failed on my truck this last fall at about 150k mi. The independent shop that did it initially quoted $2600 to replace the rubber part and the forward (easier) metal tube. I opted for a complete, one piece assembly with braiding over the rubber tube. That added another...
After reading thru the W58 recall that John Jensen posted, it looks like if your truck DID NOT get the "Approved Emissions Modification" and the settlement money, they will replace your tone wheel and flash your ECU to read the cam sensor when the tone wheel fails. If your truck DID get the...
Yes, heavier tire/wheel combos reduce MPG's - takes more power to get them spinning. Also, aluminum dissipates heat better than steel so it runs cooler - Cooler tires wear a tad slower.
Seems like these engines need to be worked hard regularly to get things hot enough for soot to burn off and clear the DPF. Since I live in Denver area, I go up I-70 into the mountains somewhat regularly in addition to the periodic road trips - seems to help keep soot burned off.
Mine is a 2015...