First maintenance issue in 11 years of ownership!!!
So starting last spring I started hearing a couple of noises. The first sounded like a rattle - but not metal, more like the sound you'd hear if something was dragging against fan. It only lasted a brief amount of time, and was gone. The second noise was more like a diesel engine sound, at lower rpm ranges typically. Very intermittent. I always run 89 octane fuel, BTW.
I let it go as the first wasn't really an issue unless the truck sat out in the cold overnight. I had my trusted local shop check things out and their best guess was something in the exhaust causing either/both. They had recommended Marvel Mystery Oil as a cleaner and I added 8 oz to the crankcase. About a week later the truck threw code P0460, related to the cat (or cats). I don't believe in coincidences so I am wondering if adding the Marvel could have caused something problematic downstream?
This morning I am changing the PCV valve, air filter, and cleaning the MAF as first steps towards resolving the light - any other thoughts/input welcome.