1999 Chevrolet Silverado 1500 "p0420" Questions

P0420 & P0430 codes 99 silverado i have a 99 silverado1500 4.8L and im getting codes P0420 and P0430? i was told it was my o2 that needed to be replaced, but theres 4 of um 2 (pre&post)on each

My 1999 Chev Tahoe will not start - Has codes p0430 and p0420 Hi Charlie,Diagnostic Test Codes (DTCs) P0420 and P0430 ar "Catalyst Efficiency" codes.  These simply mean that the catalytic ...

My 2003 1500hd Silverado 6.0L has the error code of P0420. Can you help? P0420 is a catalytic convertor efficiency below threshold, basically the convertor is not working to specs. As long as you are ...

obd2 po420 code P0420.....Catalyst System Efficiency Below Threshold (Bank 1)

code p1415 and code p0420 Checkout this link and your codes can be found on pages 7 and 19 of 30 pages http://engine-codes.com/make/chevrolet/1

gmc sierra 2003 obd2 P0420 what should i test? What size engine does your Sierra have? Usually, this code points to a bad catalytic converter but not always... since the rear (downstream) oxygen ...

...is catilytic convertor no good and 446 is an evap problem P0300="random/multiple misfire detected" P0420=catalyst efficiency below threshold (bank 1) P0430=catalyst efficiency below threshold (bank

...the convertor and the code will go away on its own after a couple normal condition drive cycles P0420=Catalyst System Efficiency Below Threshold Bank 1, This is no big deal,unless you want it to ...

...by the warranty and repaired free of charge by your dealer. For example, if you have the code P0420 - Catalyst System Efficiency Below Threshold it's very possible that your catalytic converter ...

have a 20088 fully loaded nissan quest with code p0420 plugs and coils have been replaced already drives fine https://www.fixdapp.com/blog/p0420 https://www.fixdapp.com/blog/p0420 https://mechanicbase