The O2 sensor in your vehicle monitors the exhaust gases coming out of the engine. It determines the amount of oxygen in the gases, which indicates how well the fuel is being burnt. The O2 sensor then sends information to the electronic control unit, or ECU, the vehicle's computer. The ECU then adjusts the air-to-fuel ratio to optimise the fuel combustion. Sometimes an O2 sensor fails, and you need to replace it. Once you've replaced your vehicle's O2 sensor, you'll need to reset the ECU so it can properly gather information from the new O2 sensor.
Open the fuse panel in the driver-side foot well, under the steering column, by pulling down on it with your fingers.
Locate the fuse for the ECU using the fuse diagram on the underside of the fuse panel cover.
Pull the fuse for the ECU using the fuse pullers in the fuse panel.
Turn the ignition to the "On" position but don't crank the engine (it won't start anyway).
Wait five minutes and reinsert the fuse. The "Check Engine" light will blink, then shut off. This will indicate that your ECU has been reset.