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2002 Pontiac Sunfire Question: Check engine light is on. Code PO420. What could it be?

 

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SidS, 2.2L 4 Cylinder, Beaver Dam, WI, May 23, 2013, 11:11
 Rookie

The car runs fine, smooth. No missing or backfires.

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  • Answer #1

    Greg's Orange Auto (13188 Answers) , Orange, CA - (714) 361-9386
    globalhelper May 23, 2013, 12:58
     Master

    catalytic converter is bad or 02 sensor issue

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    SidS, May 23, 2013, 13:25
     Rookie

    Is there any way to find out which it is?

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    globalhelper, May 23, 2013, 13:31
     Master

    yes scan o2 readings and see if post 02 is reading correctly as compared to pre catt o2. also measure temp going into catt and out of catt there should be between 50 and 100 degrees diff between the 2

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    SidS, May 23, 2013, 14:21
     Rookie

    Thanks!

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