I have a code that indicates O2 sensor problems. I was on the assumption that Carrera had 4 sensors. Two before the cat and two aft of the cat. I can see clearly the sensor before the cat, but the one aft is not evident. On my car, it is not on the exhaust pipe after the cat. But there is a sensor of some sort on the top of the cat. Would this be considered the aft sensor?

 

Yes, those are the post-cat sensors.They stick out from the middle of the cat. You must have a MkII.

 

The upstream (before) sensor is a couple of inches before the body of the converter; the downstream (aft) sensor is located just before the clamp between the catalytic converter and the muffler. In the following image, the upstream sensor is on the right and the downstream on the left. To clarify, your car has 2 catalytic converters, and each cat has two O2 sensors.

 

I don't have a Mk2 .It is a 2000 gen 1.But I do have at the middle of the cat a sensor and probably that is the post cat sensor Thank you for the picture but I don't have that downstream sensor in between the cat and the muffler, That was my concern.It would have been easier if so.

 

Any pics? The cats on a 2000 should look like what Schnell posted. This is the cat from Mk II with the bungs plugged. The post cat sensor goes on to the left bung and the pre cat the right bung. I suspect you don't have stock cats or someone swapped in MkII cats.

https://rennlist.com/forums/parts-ma...left-side.html

 

It sure sounds like Ahsai is correct, and your cats were replaced with the newer model. I wonder if there are any other surprises waiting for you to discover them.

 

Thanks guys. Yes ,the last picture does seem to be the model cat I have.It would then be a MKII cat. I can only assume that at one time they were changed.I do have a remanufactured motor from Porsche installed in 2004.Maybe at that time a different cat was put in. The important thing for me at this time is to correctly change the post- cat O2 sensor and you seem to have given me the answer with MKII assumption.

 

I drove it today and the check light was now off. I guess I will wait to see if it returns. I have the new O2 sensor so I will wait and keep it for another day