Hello everyone!

My check engine light has been on, i got the code and it's "Primary Oxygen Sensor".

The problem im encountering is the location of it! Most diagrams show that's it's on the headers. I have aftermarket headers and intake so it's not there. I bought the car like that. Me and my brother have been looking for one near that area and haven't found it. However we found one right before the cat. We can see it when we look staright down from the top of the engine, it's sticking out of the pipe. It's probably 10 inches before it reaches the cat. After that we tried to look for one behind the cat, but we couldn't find one. There's suppose to be another one correct? The secondary one that's suppose to be behind the cat?

Do you guys think we're looking at the primary? My brothers friend says if you changed your headers to aftermarket ones, then you'll only have one instead of 2 so i dont know what and who to believe!

btw
I have a 97 civic 2 door ex coupe, engine code is d16y8
Id appreciate any input! thanks!

 

Yes, the primary O2 sensor is located before the cat, so what you describe is what you are looking for. Perhaps the secondary sensor was removed and replaced with a simulator or the ECU is OBDI rather than OBDII.

 

Im thinking it's obdII since i used the obdII reader most of the time when i get a check engine light! Since I couldn't use the scanner this time, i just used the other method where it flashes the code. It gave me 61.

But yea, the only Oxygen Sensor we saw from the DC Headers all teh way to the cat is the one that's 5-10 inches before it reaches the cat. So that must be it? From the cat all the way to the exhaust pipe, we can't find one at all. Shoot im still looking! We're just wondering if it's hidden or something.

But just as long as it's BEFORE the cat right?

Thanks a lot tho!

 

The secondary O2 wire for my stock 00 D16Y8 feeds into a rubber plug in the chassis below the front passenger seat (I think).

 

By looking at your diagram it looks like the secondary one is located on the actual cat itself. The one we saw is on the pipe leading up to the cat. Ill check again tomorrow, maybe we just can't see the secondary because it's about 2 in the morning and we're just using a lamp. It doesn't help either that the jack we're using right now isn't that high and my cars lowered too! Ill let you know tomorrow how it goes. Hopefully it doesn't rain so I can check it out!