I have a po 420 code on my 04 canyon what is it

Why would you change any items?

Have you not googled the code?

420 & 430 are exhaust converter issues

You change no parts,you check for codes & component
test system faults using the codes, until you find a problem

code p0420 refers to cat converter system, bank 1 efficiency below threshold===causes --cat converter--wiring HO2S sensor 2

check that the cat converter is ok and replace the sensor. ( it is a HO2S sensor which will be different to a O2 sensor so get the right one )

the first code is to do with the secondary air injection optical sensor not reading correctly and i suspect it's that causing the second code which is catalytic convertor reading out of range , so get the optical sensor sorted , may be the ECU or PCM wiring or the sensor itself

po300 is a random misfire code(could be egr passages blocked under upper pleinum;plug wires;plugs or coils.PO420 is catalatic converter below threshold(converter has to be replaced)

what engine, what size. that is first question.
misfire, map ,maf, iat, ect,tps and cat fail and low coolant temps.
very odd mix there. did you pull connections, key on???????

it means they all fail a test.
DIY? or just curious?

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the question is , which is the most important.
all are cept 420, (last that, and bet goes way. later.)

reset the ECU, and see which come back.?
check all fuses.
then post codes that repeat, after fuse checks.

does the engine get fully hot running, 180F minimum?

Hi, guys! Try some other diagnostic tool to clear the code.

Thats a code for catalytic converter inefficiency. It usually means the cat is no longer able to process the exhaust gasses going through it and needs to be replaced. GM vehicles in general are no strangers to this happening.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

po 506 computer detects idle is to low.may have bad idle air control valve or needs cleaning,also make sure throttle body is clean.

Vehicle needs a Primary or first position Oxygen sensor, bank one just means it's the O2 sensor before catalytic converter

it should be mounted on the charcoal canister near the fuel tank