P CODES (POWERTRAIN) P0400 - P0499 P0420

Hello, I Have The P0420 Code On My Car. I Have Replaced The O2 Sensor And Have Run Cataclean Through It And The Code Has Not Cleared. When...

P0420 Code Sets. Replaced The Cat Because Of The Milage At A Local Muffler Shop And The Code Continues. Replaced The Post O2 With One From...

Car Has Been Well Maintained With Records. I Got A P0420 Code. Ran A Couple Treatments With Cataclean. P0420. Used An O2 Spacer. P0420....

Well I Have Been Having Problems With Knock Sensors. On Both Bank 1 And 2 And Now I Got A Code Saying P0420. And I Have Headers And A Cold...

Code P0420 Came On. This Car Has Been A Pain In The. You Know What I'm Thinking About? Dumping It But I Put So Much Money Into I Already...

We Have Replaced The Fuel Cap And Have Changed One Purge Value And After A Couple Of Days The Check Engine Light Came Back On. So, We Put...

The Previous Owner Replaced The Catalytic Converter Last Year. What Can Cause A Catalytic Converter Below Threshold? I Checked The Voltage...

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