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!

 

Is this a DX CX or EX model?

 

it's a EX model!

 

You're primary O2 sensor MUST be before the the cat. The secondary would be after. Since your car is a 97 then it normally would have an ODB2a computer which would need a secondary O2 sensor otherwise it would throw a check engine light. Are you sure the code is for the primary?

If you don't have a secondary O2 sensor and you have not check engine light then its possible that someone swapped in an OBD1 computer or wired up a way to fake the computer into think there's one.

The primary O2 sensor is used by the computer to control the air/fuel mixture the secondary one attempts to verify that your catalytic converter is working.

 

Yea we tried looing everywhere near the exhaust manifold to see if we can find the O2 sensor near there but couldn't find it. The only o2 sensor we found was on the pipe leading to the CAT. It was located on top of the pipe about 5/10 inches BEFORE the pipe went into the CAT! Do you think that's it? I have aftermarket DC Headers!

Also How can you tell if it's OBD1 or OBD2? Ive always used an OBD2 Scanner to run dianostics. Since I cant loan it out from Autozone anymore, I did it the other way where you stick a wire into the plug near the ECU. It flased 61. I looked it up and it was "Primary Oxygen Sensor".

 

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