P CODES (POWERTRAIN) P0400 - P0499

What All Should I Look At With Cat Code P0420? It Seems To Not Have A Lot Of Power At Times, 02 Sensor Possible. Bank 1? I'm Getting A...

Passed My Smog Test, And Soon After The P0420 Displayed, Took It To Dealership And They Said There Is No Problem With Cat Converter And...

These Codes, P0420 And P0430, I.E. Both Catalyst Converters In The System Show Efficiency Below Threshold, Showed Up Today. The...

I Have An 03' Cadillac Deville Base Sedan And It Is Throwing The Code P0420 (catalyst System Low Efficiency Bank 1). This Code Just Came Up...

When I Unlock The Driver's Side Door With The Key To Open The Car Alarm Goes Off: I Lock The Door From Inside The Driver's Side Door...

P0404 Has Come Up Three Times In The Last 10 Months And Has Been Reset In All Cases. Once In Sept Of 2019 And Twice This Past Week. When...

The Mil Pops Up Immediately After Resetting Battery, My Scanner Describes It As "evaporative Emission System Vent Control Circuit"...

Sorry, This Is So Long. We Are Desperate For Ideas. These Are The Events That Have Taken Place. The Gas Gauge Stopped Working A Few...

Hello Everyone, I Failed A Smog Check Due To P0446 Code. I Took Out Evap Purge Valve From Under The Hood, Applied Nine Volts To It, It...

We Replaced The Gas Gauge And The Check Engine Light Came On. They Then Replaced The Fuel Tank Pressure Sensor And The Light Went Out. It...