Code P0420 Catalyst Efficiency Below Threshold Bank 1. Emissions Test! NO PROBLEM!

If the P0420 code is combined with other codes it's always a good idea to fix them in order.

Your Catalytic Converter Should Never Have Failed. If It Did, Then You Have A PROBLEM!

To avoid catalytic converter problems, keep the engine up with regularly scheduled maintenance tune-ups and system maintenance per factory recommendations.


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Possible causes:

A damaged or faulty oxygen sensor
Fuel injectors may be faulty
Fuel injector leaks
Spark plugs may be faulty
Improper ignition timing
Engine Control Module
Exhaust pipes damage
Catalytic converter itself
Oil or Antifreeze entering the exhaust system
Cat efficiency drops below 92%
Road Damage or Broken Hangers

Products and Technique I used To Pass Emissions Test

OBD-II Scan Tool
STP Gas Treatment
STP Fuel Injector Cleaner
Cataclean
Ran Engine at High Speed / High RPM's to Burn & Blow Carbon Build up out.
Took Car Right To Emission Test Station

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