I have a code P0420 on a 1998 Olds Intrigue, I've already replaced the up stream O2 sensor and it still comes back on once the drive cycle goes through a complete cycle.
Replaced the up stream O2 sensor!
Hello and thank you for trusting me with your question. My name is XXXXX XXXXX X will do my best to help you with your Oldsmobile problem.The P0420 code only sets when the catalytic converter no longer properly removes hydrocarbons from the exhaust gases. The rear O2 sensor readings will closely match the front O2 sensor readings and they should not. The problem is not in the O2 sensors, if it were you would have different codes. The only fix for the P0420 code is to replace the catalytic converter. If you would like any additional information or have more questions please don’t hesitate to ask! Please remember to only rate my service when you are satisfied. IF you feel the need to rate "Poor Service" or "Bad Service", please stop and reply to me via the REPLY TO EXPERT button with the issue you have. I will be happy to continue further and do everything I can to provide you with the service you seek.I am not paid unless I get a rating of 3 to 5 Stars/Smiley Faces. If I have helped you with your question, please give me an appropriate rating so that I get credit for helping you.Thank you,David
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