Oxygen Sensor 22641-AA480,1924002120,25054047,22641-AA381 for Subaru

Front oxygen sensor rear oxygen sensor
The oxygen sensor in front of the three-way catalytic converter is called the front oxygen, and the rear oxygen is mounted after the three-way catalytic converter. It is generally considering that the front oxygen has a greater effect than the rear oxygen, because the front oxygen is used to adjust the density of the mixed gas, and the rear oxygen is to monitor the working condition of the three-way catalytic converter. Oxidation reaction will occur when the three-way catalytic converter is working, such as CO+02=CO2, which means that the oxygen content monitored by the rear oxygen is less than that of the front oxygen.  Otherwise, the three-way fails or the purification capacity decreases, a few vehicles will light up the fault light, prompting the owner to check or replace the catalyst.
Front oxygen sensor damage symptoms:
Unstable idling: The engine may become unstable when idling.
Increased fuel consumption: Fuel economy deteriorates, and fuel consumption increases for the same driving distance.
Insufficient engine power: The engine feels powerless when accelerating, and the speed increases slowly.
Black smoke from the exhaust: Due to incomplete combustion, the exhaust gas may contain black particles.
The engine fault light is on: The engine fault indicator light on the dashboard may light up.
There is a rumbling sound from the engine exhaust: The exhaust system may make abnormal noises.
There is a pungent smell: The exhaust gas may contain an irritating smell.