If your oxygen sensor stops working the fuel (gasoline) and air mixture will be incorrect. Usually this means your fuel efficiency will decrease -- that is, the engine will burn more gasoline than necessary. It's possible however, if it begins to run too lean (not enough gasoline for the amount of air) it can damage the engine. But, this is unlikely.
It depends on which o2 sensor.
The rear oxygen sensor looks at the percentage of oxygen in the exhaust after it has passed through the catalytic convertor. The computer compares this with the reading from the front sensor to tell if the catalytic converter is working correctly.
When the oxygen sensor goes bad, the check engine light goes on.
Oxygen sensor slow response. It means the sensor is worn out and working slowly
When a Subaru has a faulty O2 sensor the fuel management is out of whack.
When an oxygen sensor goes bad a car will burn gas at a higher than normal rate because it will not be producing as much power as before. The oxygen sensor checks the amount of exhaust.
From my experience working on Chrysler,Dodge,Jeep vehicles. The only good oxygen sensor is from the dealer.
The vehicles don't run right
It is the downstream sensor on one side of the engine that tells the computer how well the catalytic converters are working.
The check engine light will illuminate. The code(s) will direct you to the faulty sensor.
There are two oxygen sensor for Mitsubishi Outlander. Front Oxygen Sensor and Rear Oxygen Sensor
If the vehicle was built with an oxygen sensor, you will need an oxygen sensor.