420A OBD II codes P0420 P0442 P0455 yay! :/

[ForsakenLash]

Ok, so today for fun I decided to hook my scanner up because I remembered my CEL doesnt work and guess what..... I pulled 3 codes!!! /sarcasm.....


Codes are as follows:

P0420
P0442
P0455



I know the last 2 are probably my gas cap.... so that will be getting replaced.... however I am curious if it is possible that these 2 codes are causing the P0420 code as well? If so yay for me, but if not where do you recommend I start? I do not have any aftermarket exhaust equipment anywhere on it that im aware of, so what is the best place to check first?

 

[synthetek]

The P0420 code is a bad cat or rear o2 sensor its not related to the evap codes.

 

[jimsgsx]

How is your car running?

 

[ForsakenLash]

It runs fine with the exception of slightly poor gas mileage

 

[briansmith]

It's not a rear o2 pa 420 is cat efficacy this means the front o2 voltage is and rear o2 voltage are matching look at the data list on a wave for for front and rear o2. Rear o2 voltage should be between 3.0 and 4.0 steady so a line. Front should be sweeping somewhere between .5 and 5.0 volt. If rear is sweeping the cat is not doing its job. Most likely the case. So many people tell u oh 420 codes are o2 codes no that is a cat code and cat code only. O2 codes are o2 slow activity or heater circuit malf on no response

 

[ForsakenLash]

Ok, so how do I fix it?

 

[briansmith]

If the wave graph shows both O2 sensor patterns sweeping and the rear not staying steady then you have a inop cat and it must be replaced. Other 2 codes are evap small and large codes. I see very few gas caps fix these codes. Do not replace the whole cap the aftermarket caps fitment sucks. If you suspect a leaking cap get a replacement. Remove the o-ring and install it on your factory cap. The caps don't wear out the o-rings do. Or take your factory o-ring off flip it over and install it back on the cap.

If codes persist you will need to preform a smoke test with nitrogen DO NOT USE COMPRESSED AIR. If you use just air you have now made a very large bomb.

An old tech told me once cats don't die they are murdered. If your cat is bad something killed it 1 could be time. These cars see a lot of abuse and time can kill it. But most likely a modded turbo car. Something killed it too rich or lean fuel trims, rich you're dumping raw fuel into the cat, lean cats running hotter than it should. Misfires will also dump fuel into it. This is why the check engine light flashes for a steady misfire only. No other code causes the flashing check engine light. It's screaming look at me you're murdering your cat. Cats have no moving parts to wear out it's a chemical reaction between the platinum and exhaust gasses to take harmful fumes and convert them to nitrogen, carbon dioxide, and H2O but for this process to happen the chemicals must be balanced.