I had previously fixed my P0420 which was the passenger side, now the driver side went on ... It was costly to fix 500 was the best deal for original cat ... now the check engine light had went away but the car is running rich and it idles when its cold at 1.5-2.00 .... any suggestion of what should I do ? no leaks that I can hear ... it was a leak at the gaskit but I fixed it then this code went on ... what should I do? plz help

 

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What kind of MPG is it getting now? You already did the gasket , go back and verify the sealing. A leak at the midpipe will still change the value the O2 sensor can read.

If good, replace the top bank O2 sensors (may as well do the second bank sensors since you are under the car and to be sure IMO), clear codes by removing the neg battery cable for about 30 seconds. Drive car and see if the P0430 returns, if it does then you know the cat will need attention.