Hi guys. I'm new to the site...wish I knew it existed in the first place! :-) Anyway, my 54K 2005 Mazda3 got a check engine light today so I drove it over to my local Auto Zone. They retrieved the code and said it was PO144, or an Oxygen Sensor. Anyone know what that is? They said the part is $122.99. Should I take it to the dealer? Is it still covered? Is my car going to blow up, or do I have some time? :-) Any info you could provide I would greatly appreciate. Thanks!