CHEVROLET P CODES (POWERTRAIN) P0400 - P0499

It Started Out With A Bad Gas Cap. Went To Auto Zone And They Sold Me The Wrong Cap That Wasnt Pressurized. I Drove For 3 Weeks Like That....

Got P0430 And P0420 Codes Show Up For Inefficient Cat. Replaced Post Cat O2 Sensors With No Luck; Check Engine Light Came Back. Took To A...

My Car Listed Above Ls Model, Is Throwing Code P0420, Haven't Noticed Anything Acting Different. I'm Just Curious As To How I...