I have a 2006 kia sportage I keep replacing the o2 sensor and the chem engine light keeps coming back could it be the Cadillac converter

I really wouldn't worry about the light.........just keep driving it and as long as its driving fine

So where to start....what is the code? Are you replacing the same sensor or one of each so far? How many miles on car? If this is a V6 you have as many as 4 sensors. 2 upstream and 2 downstream. I would not condemn the catalytic converter just yet as these sensors are a maintenance item as they have a life expectancy of 80K - 100K. And when you have a code for 1 it is best to replace all of them as they affect each other and you run the risk of lowering the life of a new one by keeping old ones on there with the new. You will get a CEL for the others soon. Sorry but lots of variables to your question and you don't want to replace the catalytic converter $$$$$

I would not just keep driving it with a warning light. If you value your $/investment. You are wasting fuel and carboning up your engine and lowering its life expectancy by doing this. You will be changing out the catalytic converter soon with this philosophy