The Subaru Oxygen Sensor in your exhaust system collects the data on the levels of oxygen in the spent fuel that your engine uses in the production of power. This data the oxygen sensor collects is then compared to the oxygen levels in the air surrounding the Subaru and sent to the on board computer where it is analyzed.
The data collected by the oxygen sensor in its readings is used by the onboard computer to help determine the correct air to fuel ratio that should be used in the combustion chambers so the maximum power level of this combustion in the Subaru can be achieved in the most efficient manner.
When the signal from the Subaru oxygen sensor is no longer reaching the on board computer, the check engine light will become illuminated on the dashboard informing the driver of a failing sensor. Once the code or codes are retrieved from the onboard computer, the faulty component can properly be identified. When the code for the oxygen sensor is retrieved, the owner of the vehicle should first look to see if the wire connecting this sensor to the computer is still connected and is undamaged. If the wire is in place then the sensor should be replaced so the fuel allotment calculation can then be done in the correct manner.
The first step in the replacement procedure on your Subaru is to disconnect the battery. This will prevent any possibility of the person making the repair from becoming shocked by an electrical current. At the same time it will clear all of the codes the onboard computer has stored in its memory. Once this is done and the new oxygen sensor is in place the data collection of this sensor and the other ones can commence as designed to provide the most efficient use of the fuel in powering the vehicle possible.