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Code P0420

2K views 2 replies 2 participants last post by  zimzam 
#1 ·
Has anyone had issue with this code P0420? I read the code with obd scanner and it says"catalytic efficiency below threshold bank 1." I am assuming this an upstream bank 1 O2 sensor( located on the back side of the engine). Can anyone shed some light on it? Thank in advance!
 
#2 ·
this is an infamous code asking for replacement of cat, typically. It might be due to other reason as well. you can try to clean up the cat.
 
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