clogged fuel filter, choked cat converter.
O2 sensor is like a bulb element enclosed in a perforated steel tube, it sense the exhaust gas temp which fluctuates due air-fuel ratio. It malfunctions and throw CEL when fuel is too lean and exhaust gases are over heated due to absence of correct amount of air at ignition producing high temp gases at exhaust, continuous over heating of O2 sensor, result in failure.
when replacing an O2 sensor it is highly recommended to clean cat converter as well.
since O2 sensor is as expensive as a cat converter, Locally CAT converter is cleaned and O2 sensor is dip cleaned with petrol. however can be sourced from scrap yards.