The car runs fine, smooth. No missing or backfires.
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2002 Pontiac Sunfire Question: Check engine light is on. Code PO420. What could it be?
catalytic converter is bad or 02 sensor issue
ReplySidS, May 23, 2013, 16:25Rookie
Is there any way to find out which it is?
Replyglobalhelper, May 23, 2013, 16:31Master
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
ReplySidS, May 23, 2013, 17:21Rookie