My dealer told me today my CE light for the O2 sensor is caused by my full exhaust with stock ecuThat was what mine did. This started last fall with a check engine light. I was getting a check engine light all the time. I would bring it in and the dealership would clear the code and tell me it was an O2 sensor and to not rev the engine hard when cold (I don't). I got the check engine light again, and said screw it about bringing it in. Then it began to not even want to idle. That is when I found the broken hose. I replaced it and it started right up and the check engine light cleared itself.
Then got the check engine light again a few days back, that's when I replaced the clear plastic hose that had yellowed and hardened with a new piece. CE Light cleared itself.
I left it at the dealership since I had to leave for work for 3 weeks. So I won't pick it up until after the 14th.