Trouble cod P0420 - 2008 Subaru Impreza Wrx

codes are OBD codes and are available on line free. copy and paste

https://www.yourmechanic.com/article/p0305-obd-ii-trouble-code-cylinder-5-misfire-detected-by-jay-safford

https://www.yourmechanic.com/article/p0446-obd-ii-trouble-code-evaporative-emission-control-system-vent-control-circuit-malfunction-by-spencer-clayton

https://repairpal.com/obd-ii-code-p0446


https://www.yourmechanic.com/article/p0420-obd-ii-trouble-code-catalyst-system-efficiency-below-threshold-bank-1-by-jamahl-walker

https://www.obd-codes.com/p0420

P0420 is a code for the catalytic converter. It has failed the efficiency test. See this post for the full story on P0420 trouble codes

https://ricksfreeautorepairadvice.com/p0420-is-it-the-catalytic-converter-or-the-oxygen-sensor/

https://www.fixdapp.com/blog/p0420 https://www.fixdapp.com/blog/p0420 https://mechanicbase.com/trouble-code/p0420 https://mechanicbase.com/trouble-code/p0420

Pesky PO420 Codes - Eastern Catalytic

www.easterncatalytic.com/education/tech-tips/pesky-p0420-codes/

One of the most annoying is the persistent PO420 diagnostic code (Catalyst System ... not only shows its teeth when the catalytic converter is on the blink, but can also be ... Most, if not all, catalytic converter failures are caused by a problem or ...

P0420 Error Code: Catalyst System Efficiency Below ...

www.obd-codes.com/p0420

Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency ... If they have failed, it is likely due to something else that caused it to fail. ... the catalytic converter is broken or failed, it may be restricting the exhaust which will ...

explaining trouble codes po420 - po421 - Discount Catalytic ...

Needs a cat and need to check the injector and coil. Coil most common on that model

P0420 OBD II Trouble Code

The above link will provide a lot of inforamtin about the P0420 trouble cdde.

P0420 isnt a misfiring code; this code P0420 is refer at Catalyst System Efficiency Below Threshold (Bank 1).

Feel free to contact us if you need additional details to volve it clicking the link.

Two new o2 sensors. I use Denso

http://www.obd-codes.com/p0420

TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
there is a service bulletin for this.

http://www-odi.nhtsa.dot.gov/cars/problems/tsb/results.cfm?start=1&SearchType=DrillDown&type=VEHICLE&year=2005&make=CHEVROLET&model=COBALT&vehtype=PC&typenum=1&component_id=0&summary=true

Here is the trouble tree for that code it is most likely a bad cat but follow the trouble tree to see where it lead's you.
DTC P0420 or P0430

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview\Diagnostic Starting Point - Vehicle
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0420

* Catalyst System Low Efficiency Bank 1

Important: A new converter with less than 100 miles on it may set DTC P0420 or P0430 due to out-******* of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition. Hope this helps