DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

P0420 - CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)

Description:	This DTC sets when the bank 1 catalyst system efficiency is below the acceptable threshold.
Possible Causes:	Damaged heated oxygen sensor (HO2S) Exhaust leaks Damaged exhaust manifold Damaged catalytic converter Oil contamination Cylinder misfiring Downstream HO2S wires incorrectly connected Damaged exhaust system pipe Damaged muffler and tailpipe assembly Leaking fuel injector Oil contamination of the catalyst Damaged turbocharger Base engine concerns
Diagnostic Aids:	Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage capability. As catalyst efficiency deteriorates, its ability to store oxygen declines. Refer to CATALYST EFFICIENCY MONITOR , for additional information. Diagnose any base engine concerns. Refer to the appropriate Engine System article.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
All	GO to PINPOINT TEST HF .