PO420 small EVAP leak

[sdeeter19555]

I'm getting this code popping up from time to time, very inconsistent as it may go several weeks and many miles between popping up to driving my 50 mile commute home the same day. I can easily clear it, but I want to address the issue. Truck is a 2012 flex fuel, 2500hd, 6.0l.

 

I spoke with the garage that does a lot of my work, and he told me to try a new gas cap. This was after cleaning the sealing surface of the filler neck (which was dirty, but not corroded or rusted). I ordered a cap last week (AC Delco replacement from RockAuto), verified it was the same part number as the old one (there are multiple versions of that yellow cap), and installed it. Code popped last night on the ride home...probably 400 miles after installing the new cap.

 

Short me taking it in to have them smoke test the emissions, are there any other known trouble spots on the 2500s that can cause this?

 

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[kstruckcountry]

The hose are crappy plastic. They can crack. You might not be able to find the hole yourself, but replacing all the rear ones with rubber hose and hose clamping them could help? I'd also check under the hood too.

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[Justin101714]

P0420 isn’t an evap leak code. Are you getting confused with a P0442 or a P0455. Those are leak codes. P0449 is a circuit issue within the evap system.


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[sdeeter19555]

My bad, I remembered the wrong code...it is 442.

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[jhplak325]

It could be anything with that code. Gas cap, vent valve, purge valve, hoses, cracked sending unit etc...

 

Best bet is to get it smoked, if not then you are just throwing parts at it. 

[sdeeter19555]

Thanks, that's what I suspected. It never hurts to ask because sometimes there is a very specific cause...

I want to get the brakes bled and fuel pump replaced anyway, probably wait until December and have it all done at once.

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[jhplak325]

Not a problem.

 

I had a 2009 Silverado 2500HD that would get that code all the time. Replaced gas cap and that lasted about a week or so. Then replaced the purge valve and that lasted for a few months. 

 

Code would come and go all the time. Sometimes I would reset it and other times it would clear on its own. Don’t know what the actual fix was due to trading it in. 

[8lugCT]

Funny. My trucks is now telling me to tighten gas cap periodically. No code but sounds like a similar issue

[sdeeter19555]

Another twist, running e85 and no light for weeks!

Steve
2012 2500hd