https://www.ifixit.com/Answers/View/105660/Mazda+3+Check+Engine+Light+P0126+&+P0128
SOLVED: Mazda 3 Check Engine Light P0126 & P0128 - 2004-2009 Mazda 3 - iFixit
Ingrid, take a look at this information from the service manual. The actual installation is not a horribly complicated job and definitely doable: "DTC P0126...
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