green horn from iowa.
hey everyone..im a newbie to the site so i apologize if im posting this question in the wrong place..but i have a 2008 eclipse w-the code po421.now i know that it is an o2 sensor and i believe its in bank 2 but when i went to order one i was asked 'front or rear' and 'upstream or downstream'..can i know which one it is by the code given or do i need to get specific readings from each individual sensor.
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