Noticed the check engine light upon starting, today. Running great!

2014 IS 350 f-sport with 73k miles. WTH could it be? Any thoughts?

 

Without knowing what the code is, it could be any of a few hundred things.

Did you fill the tank within a day or two of the light coming on? Check the gas cap to make sure it's tight.

 

go to an auto parts store, use their ODB2 scan tool...get the CEL Code and go from there.

 

Better yet, maybe just buy a simple one. Worth having around, I use it for all kinds of other things analysis and diagnostic (usually other people's cars)

I think my Carists Bluetooth OBDII was $30 maybe $20, and my other pluggin one was like $15.

Tried a China shipped WiFi one, threw it out.

 

probably O2 or air fuel ratio sensor. friend had this happen to his car too (2014 IS250), had it happen to my old corolla.. think Toyota notorious for this sensor failure.. Dent in the pocket too.. car runs normally even if this sensor goes bad, just annoying engine light