1997 buick skylark check engine light, code is po420 can anybody help me?
Code P0420 is for a" Catalyst System Efficiency below threshold" ( bank 1 ) most commomn is from a clogged Cat. Converter , but you can have the exhaust sys. tested for excessive back pressure and if it's too high you would need to replace the Cat. Converter assy.
H.T.H.
John
Guyopel
The early bird gets the worm but the second mouse always gets the cheese.
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