oxygen sensor help needed

[zephex]

I had to replace the catalytic converter on my 2006 Chevrolet Cobalt. It is the LS version not the SS version.

when I took off the old converter, the oxygen sensor was behind the converter. It was between the converter and the exhaust pipe. New converter I installed has 2 holes for sensors. One in the same place as the old one, and then one before the actual converter up near the flex pipe.

the converter installed fine. But I think we may have damaged the o2 sensor during changing. The check engine light came on a few hours after replacing the converter. I looked online for a new sensor and everything I have found shows that the sensor goes into the hole before the converter. If this was the case, why was the o2 sensor after the converter on the original one we replaced?

I guess what I am asking is where does the o2 sensor on my car truly belong? Does it go before the converter or after it? I can plug the other hole using a spark plug or something like that. I just find it odd that the original o2 sensor was behind the converter but everything that I find online shows that it goes before the converter.

I am NOT a mechanic and I am just learning how to work on cars so any help will be appreciated

[maxwedge]

What was the code, all vehicles have a sensor in ft of the cat and after the cat. The code will tell us what is happening.

[zephex]

I don't know the code yet because I don't have anything to read it. I just ordered something to read codes today. I replace the converter because it was cracked and I could tell where it was. The original converter only had one sensor. And it was located behind the converter. It did not have two. the only sensor was located after the converter between it and the exhaust pipe. If my car does have two centers, then the other one is not located on the converter itself. Maybe it is somewhere else. I guess that is why I'm so confused. I put the old sensor behind the converter on the new park just like it was on the old part. I'm only assuming we damage the o2 sensor but until I get the code reader I won't know for sure

[zephex]

another guy told me that the car does have two sensors but the upstream one is not located on the converter itself. That is why I only had to work with one.so now it is only two possibilities. One either the sensor is bad from us changing it or 2, the converter that I bought is just a piece of crap and it is not getting the job done. I am not sure how I will be able to tell which one is the problem. I should have something to read codes later this week

[Tech II]

The front O2 sensor is probably located in the exhaust manifold .....

A scan tool that can plot wave forms, is what you need....places like AutoZone, you can rent them.....plot the front and rear....if the rear "mirrors" the front, bad cat......

the front should be constantly changing, while the rear should be very slow to change, may be staying high or low, depending on whether the cat is storing oxygen or not......but it should not be changing rapidly like the front.....

[tomj76]

You will get a code by installing the rear sensor in front of the converter, because the PCM is looking for a zero oxygen reading from the rear sensor. This sensor is there to verify that the converter is working correctly.

The front sensor gives a different reading because the oxygen level is higher there. The front sensor is used to adjust the amount fuel that goes into the engine and keeps the fuel/air mixture ratio at the optimum.

Also, the extra hole must be plugged, or a code can be generated. The autoparts store should be able to help you with that.