Hey everyone! Long time since I posted on here! My inspection came up recently, so I took it in and apparently it threw a crapload of codes, and one of the oxygen sensors wasn't even plugged in. I decided to do a little investigating, and saw an empty connect where the downstream O2 sensor is supposed to be. Unfortunately, there's no place for a sensor to be plugged in (Custom/Magnaflow exhaust from PO). My question is: Is it absolutely necessary for the downstream O2 sensor to be there? I've owned the car for the past two years like this, and passed inspection multiple times. So why is it an issue now all of a sudden?

 

if you passed emissions before I'd check your cat and how long since a tune up?

 

So you are missing an o2 sensor and your check engine light is not on? Did the PO have a custom tune done to keep it off? Guessing the codes showed up when they plugged in an analyzer.

The rear o2 sensor is there to monitor cat performance without it you will never get a ready for test on the IM. That should bring the emission test to a quick fail.

However it really won't affect engine performance.

Most any competent muffler shop can weld in a sensor bung so one can be connected.

 

Turns out the PO did an EGR delete and part of the Magnaflow catback does not have an area for an O2 sensor. Took me this long to realize it...