I see a TST listed in your mods. The TST has caused the P0336 code for years. Some trucks throw that code a lot, some every now and then and some never. Mine will throw it about twice a month. Never really affects performance, just a nuisance. I just clear it on go on.
I get that sometimes with my TST if I get on it hard and the RPMs are below 1500. Just clear the code with Smarty and don't worry. Like others say it is very common with using TST.
No I checked it theres no mud or anything on it....must be the tst...but ive had it on there for probly a year and it just now threw the code last week.