Does the light go out after a few minutes? my service agent said that if the light goes out then the computer is happy there is no longer a fault but logs it in the memory for diagnosis later. I had the same lights come up a couple of times after i had a Tubi fitted they did change the oxygen sensors as a precaution but they did light up again, seems to have settled down now. They offered to pull the car in but as it was in intermitent fault they advised me to monitor it and if it became more than that then they would collect the car still enjoying the car 1000 miles latter