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My new headers and exhaust led to error codes P0420 & P0430, which translate to:
Catalyst System Efficiency Below Threshold (Banks 1 & 2).
Cleared it once, but it came right back. Is this coming from the O2 sensors, or somewhere else? I'd like to know before I take her back in the shop, so I don't have to watch the wingnuts scratch their heads for a half hour.

Thanks in advance,
Mr M
Catalyst System Efficiency Below Threshold (Banks 1 & 2).
Cleared it once, but it came right back. Is this coming from the O2 sensors, or somewhere else? I'd like to know before I take her back in the shop, so I don't have to watch the wingnuts scratch their heads for a half hour.
Thanks in advance,
Mr M