CODE 0420 ON A 2002 MONTE CARLO SS 3.8L ALSO RESONATOR PIPE IS LEAKING WILL THAT CAUSE THE CODE
3 Answers
migration_judge_roy answered 11 years ago
"catalyst system efficiency" yes, that's you buddy. Get it repaired!
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same hear, get leak fixed, causing oxygen sensor to read wrong and causing computer to set the code.
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Hey @TIMFLYF! I was wondering if fixing the resonator cleared the P0420. Many people say that a leak downstream of the Cat will not cause a code. I have feeling it might. I'm facing the same situation you were facing, so I'd appreciate your feedback!
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