I have a 2012 Mazda3 2.5L. Specifically (2.5L I4 EFI Engine) I got the P2243 OBD code (with the associated engine light). Indicating an issue with O2 sensor Bank1 Sensor 1 (upstream O2 sensor). I ordered the replacement part and decided to get to work. My issue is I can't readily find where the sensor is installed. I watched various YouTubes with the 2010 engines (upstream O2 sensor looks pretty easy to access). Looking in the same general area in my car - around the firewall backside of the engine and I don't see anything like an O2 sensor in my 2.5L. I would love to see a picture of where this thing is. Alternatively, a good description would be great. I am starting to guess that the sensor is in a really hard place to get to. Any help to clue me in is much appreciated!