Where is the o2 Sensor located?

Hello, the front sensor (before the Catalytic Converter) is an A/F ratio sensor, air/fuel ratio sensor and is a wideband type sensor, the rear oxygen sensor is a narrowband oxygen sensor. They both work differently. Are any codes setting in the engine control module (ECM)? I'll post the wiring diagrams to identify the two sensors. There should be a code setting if the Readiness monitors are not passing.

Here are the wiring diagrams for the oxygen sensors, the 2nd one is the OEM diagram. But if you have access to a scan tool, I would check the live engine data to see if there are any codes stored, or if the engine is running rich or lean. The Long Term and Short Term Fuel Trims will tell you a percentage, either positive or negative, and this is the amount of compensation the ECM is making for a rich or lean condition.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here are the locations of the primary and secondary oxygen sensors. Check out the images (below). Let us know if you need anything else.