Troubleshoote code P0420

98Cobretti

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Sep 24, 2002
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Orange County
I got this code and it came up as: The PCM has determined that the catalyst system efficiency for bank 1 is below threshold for the current engine operating conditions. (bank1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank).

After I got the code, I bought the Mil eliminators and thought that it was fixed, but I just got a check engine light again the other day, and havent had it scanned yet, but am pretty sure it is the same thing. So is this a malfunctioning catalytic converter, or a malfunctioning O2 sensor? Help!
 

TLush

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Feb 24, 2002
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174
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Independence MO
It is possible your O2 sensors are going bad. That code comes up all the time on mine (Cats are gone). When I get around to getting a chip I will have them program the rear O2's out of the diagnostic loop.
 

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