2002 XC70 Oxygen Sensor

[Stephen0523]

Hello. I have been just curious as to when I would know to replace the oxygen sensor on our XC70.
Do I just leave it and WAIT an alert comes up?

Thanks

[oragex]

The front one is responsible for the mixture, but it won't trigger a check engine if it's old and all messed up (unless the heating element that's inside also fails).

So it's up on you. If the gas mileage is great, don't touch it no matter how many miles you have on the vehicle.

A side note, the O2 sensor only works when there is acceleration, i.e the gas pedal is moving while being depressed. I believe, when the O2 fails it will cause high fuel consumption especially in slow traffic kind of situation, of driving with lots of stop and go.

And another side note, poor gas mileage is also caused by quite a few other components, so better not jumping first on the O2 sensor without checking the other parts. A partially restricted fuel injector will also cause sharp drop in gas mileage (putting these in a ultrasonic cleaning machine will fix such issue).