thanks DocDoug, think i didn't ex plane my situation right. car is totally stock i bought it new,and no issues now with MIL/DTC. runs good. awhile back i had my first engine light at 40,000 miles it was a P0301 and P0456 all fixed and running good. while i was working on the fix i found a youtube site showing how to remove the upstream O2 sensor on a 2013 elantra 1.8L the sensor on his car was easy to do on top on exhaust sticking out of the heat shield. i looked at mine not there it lower down the header and has to be removed from the bottom side. this is original never been modified. my elantra is a 2013 limited and i found a youtuber with a elantra GT the hatch back car with the O2 located down there, leading me to think Hyundai maybe interchanged these engines. all no big problem just odd to me.