P CODES (POWERTRAIN) P0400 - P0499 P0420

Hey, Guys I Replaced The Trans. Bearings, Took Car For A Ride, The Engine Light Came On, I Pulled The Code P0420 Cat. Eff. Below Threshold...

Hi, I Have Been Battling This P0420 Code On My Car (gt Model) For A While Now And Was Hoping Someone Would Have Some More Insight On The...

What Causes This Code And How To Diagnosis The Causes?

The Catalytic Converter On My 99 Miata With 43k Miles Was Replaced A Month Ago. Last Week, The Check Engine Light Came On And I Pulled The...

I Had A Tech Hook Up The Machine And He Gave Me This Code. P0420. He Said It Was Catalyst Or The O2 Sensor. Can U Help Me

I Removed The Cat Converter, But There Seems To Me No Damage Visible. Please Advise

I Bought My Car At An Auction So I Did Not Know Anything About It Or What It Had Been Through. So When I Picked It Up No Water In The...

My Check Engine Light Comes Once Every Month. The Code Is P0420. Can I Test The Rear Cat By Checking The Inlet And Outlet Temp Of The...

P0420 Was On, Cats Were Replaced With Bosal California Approved Cats As Well As New Denso Sensors. Readiness Set, No Codes For Several...

I Saw Several Messages Posted On This Issue And Wanted To Make Sure I Fully Understood What The Issue Is And The Steps To Correctly...