Hey everyone, I know this is months later but I just wanted to give everyone an update. The problem turned out to be electrical and it stemmed from when I had my engine replaced. When I had the mechanic run a test on my car I only had one of the bank one and two sensors show up, so basically only one of the 4 sensors was showing up. The mechanic reset my computer and all of them showed up and the CEL cleared. After driving the car for about 20 miles the CEL came back on and the error code p0136 showed up. I had the bank 1 sensor 2 replaced and my CEL is finally off. Thanks for the help and I hope this post helps someone who may have a similar problem.