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Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011
Diagnostic code produces P0420 catalyst system efficiency below threshold-Bank 1. Probable causes are listed as follows: 1-air leak in exhaust before rear 02 sensor, 3-Fuel system fault, 4-faulty catalytic converter.