Honda O2 sensor

1997 HONDA CIVIC
4 CYL • FWD • MANUAL
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GARROWJ
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I have to repalce a bad O2 sensor, but when I went to check on the cost there was an upstream and downstream one. How do I know which one is bad or is it just normal to always change out both?
Jan 16, 2011 at 4:35 PM
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KHLOW2008
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The trouble codes would indicate which O2 sensor is faulty.

Such components does not require both to be replaced at the same time but usually they have a life span and if one fails, there is a possibility the other might go off anytime. Personally I would not replace anything unless it is faulty.
Jan 16, 2011 at 5:03 PM