Subaru OEM Rear Oxygen Sensor Subaru STi 2008-2021 | 22690AA850

This rear oxygen sensor is specifically designed for your Subaru STi from 2008 to 2021. It plays a crucial role in detecting the oxygen concentration in the exhaust gas. When the air - fuel mixture is lean (more air), there's more oxygen in the exhaust. Conversely, a rich mixture (more fuel) means little oxygen in the exhaust. By sensing this oxygen level, it helps determine if the air - fuel ratio is leaner or richer than the ideal stoichiometric ratio. The sensor features a zirconia tube (ceramic). When there's a difference in oxygen ion concentration between the inside and outside of the tube, it generates voltage. Platinum coating on the tube acts as a catalyst and electrode material. The sensor housing connects to the exhaust pipe, and the inside links to the ECM via a harness. A ceramic heater is added to boost performance in cold conditions. When a rich mixture burns in the cylinder, the platinum on the zirconia tube uses up most of the oxygen, creating a large voltage. A lean mixture results in less oxygen use and a smaller voltage. Near the ideal air - fuel ratio, the oxygen concentration and voltage change significantly, allowing the ECM to easily figure out the air - fuel ratio. The sensor's output stabilizes at around 300 to 400 °C (572 to 752 °F). Note: Subaru of America only warranties parts installed by a CERTIFIED Subaru Dealership, and the part must match the vehicle VIN.

Using this rear oxygen sensor in your Subaru STi is easy. First, make sure your vehicle is turned off and cooled down. Locate the exhaust pipe and find the position where the old sensor is installed. Carefully remove the old sensor and install the new one in its place, connecting the harness to the ECM. When driving, the sensor will automatically start working to detect the oxygen level in the exhaust. For maintenance, it's a good idea to have it checked during regular vehicle servicing. Keep an eye on your vehicle's performance. If you notice any changes like decreased fuel efficiency or rough idling, it could be a sign that the sensor needs to be inspected. Also, remember that for warranty purposes, have the sensor installed by a CERTIFIED Subaru Dealership and ensure the part matches your vehicle's VIN.