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hi guys, have recently bought a 40,000km nc2 2010 model auto. The previous owner told me there had been an o2 sensor changed under warranty. The check engine light has come on and dealer has hooked up and told me it has a faulty o2 sensor and that there are 2 of them. Of course dealer is happy to charge heaps to rectify!

Anyone have any experience of this? How worried should I be (I should I ignore the light) Any clues on identifying which o2 sensor and any economic suppliers of same?

Thanks

How long ago did the first sensor fail? Seems like there's something else causing them to fail. I suggest Mazda would expect their replacement O2 sensor to last longer than yours has, they should offer a free replacement (and find out why 2 have died so far).

Obviously the dealer didn't say which O2 sensor is gone otherwise you wouldn't ask.
If you know someone with a scan gauge the code thrown will tell you which one is faulty.

They're not cheap from Mazda, you can pick then up from Amazon in the US way cheaper. The front one is dearer than the rear but it is usual the rear that goes.

To get rid of the light, remove one lead from your battery, turn the ignition on and push the brake pedal for 30 seconds to drain the ECU. Reconnect the battery and the light should be off, until it reads the fault again.