I changed my only upstream oxygen sensor yesterday. Nothing wrong with it other than it has over 100,000 miles on it. So out with the old in with the new. I drive it 60 miles exactly and the CEL comes on. The code is P2237. Positive circuit open on my new oxygen sensor. So I clear it and drive another 40 miles or so. CEL comes back on. The O2 sensor for this car is not cheap. The parts store will not do anything except sell me another one. So I went online and matched up the numbers on the old NTK brand O2 sensor and ordered the exact same one that came out. That "should" get the car back to normal. The parts store sold me a "direct fit" sensor. However, my car is one of two variations (low emissions or ultra low emissions) apparently it matters. The weird thing is I gave the VIN to Hyundai and they couldn't tell me which version it is.
Edit:
Did some research and I have the ULEV (Ultra Low Emissions Vehicle) not the SULEV (Super Ultra Low Emissions Vehicle) so I get the extra 5hp. Also, I verified the correct oxygen sensor and I for sure ordered the correct part. The parts store gave me the wrong part but I am still stuck as it is an electronic part... meaning no returns once installed. Oh well, I will make the $160+ back Monday.