So my girlfriend's gotta CHECK ENGINE light on. I ran the scan tool on it and it's P0411. Been doing some looking around and I've seen a lot of stuff about a DPFE sensor. Now I know nothing about any emissions or EGR or any of that crap. So I read a few things about secondary air intake or something along those lines. So basically -- does the DPFE sensor need to be replaced? How much (roughly) is one? And where the hell is it? As always -- thanks for the input.