Where is the O2 sensor located in the 2003 Toyota Corolla?

There are two 02 sensors fitted in the 2003 Toyota Corolla. They are located right before and right after the catalytic converter. Each sensor is about the size of a spark plug and protrudes into the engine exhauSTStream. The primary function of these sensors is to determine the level of oxygen in the exhaust. With these sensors, the engine makes the required adjustments for the smooth burning of gas and to achieve maximum efficiency. Also, one of the reasons for a check engine light being on is a fault in o2 sensor. So do remember to get them inspected on occasion, as Your car won't pass an annual inspection if they don't work well.