Code P0455 and the Gas Cap
 

The truck started throwing code P0455 last week after warning me to tighten my gas cap. So I checked the cap, cleared the code...a day or so later same message and same code.

It's come up three times now so I thought I'd throw this question out to the masses: Has anyone gotten this error and actually found that REPLACING the OEM gas cap resolved the issue? Or is the problem more likely to be elsewhere...charcoal canister, purge vent solenoid, etc.

I mean the cap doesn't see a lot of action...screw it off, screw it on once a week and it's protected from the weather behind my fuel door. Plus I just had it checked twice by the emissions testing center last month and it checked out both times. Don't get me wrong, I'd love for a new cap to resolve the issue...seems like a cheap fix; but I just wanna see if anyone else has went down this road.

Re: Code P0455 and the Gas Cap
 

Mine did the same thing, then it started doing 0449's instead...

here is the thread on what solved it for me..
http://www.elcovaforums.com/forums/s...ad.php?t=41945

Re: Code P0455 and the Gas Cap
 

P0455 is an evap system large leak detected. Could be a broken evap line, cracked cannister, purge valve or vent valve stuck open. Tough to find without an evap smoke machine and a scan tool to seal system.

Re: Code P0455 and the Gas Cap
 

Replaced cap and solenoid (under the driver's side next to the frame)...thought I had it. Nope...still gettin' the 455.

Which is the next logical part to check? Or at this point is it just better to have the dealer do a smoke test and be done with it?

Re: Code P0455 and the Gas Cap
 

Hi not that is going to help you with your code problem but i just bought a smoke machine today made buy redline. I used a buds to check for a intake leak on my bike after that i had to have one. They work great for checking for leaks in evap systems also wind noises and intake and exhaust leaks just to name a few. :jump: :jump:

Re: Code P0455 and the Gas Cap
 

Now I'm getting P0455 and P0496 High Purge Flow...blah blah. I guess it's time for the smoke test.

I've also notice on my last three gas-ups that immediately after putting gas in the tank (whether it was a complete fill-up or not) when I turn the key the engine cranks really fast and starts to start, but then putters out (like it's not getting any gas). When I turn the key a second time, it gets a little better and almost idles, then putters out. On the third try it usually starts after a few cranks but idles rough for a bit, then it's fine and doesn't act up again until I put more gas in.

WTF?

Re: Code P0455 and the Gas Cap
 

I'm thinking maybe the purge valve up front needs replaced...$40 (GM 12581282).

I was poking around on a Cadillac forum where the same code and symptoms were discussed: "The first time it happened was after stopping to refuel after being on the road for about 4 hours. The car wouldn't start, even after letting it sit for a bit. Finally, I pressed the gas peddle all the way down and it fired up (acted like it was flooded)."

The Cadillac tech reported that this was a "condition that we used to refer to as 'flow during non-purge'. Basically the engine is sucking fuel vapors from the canister into the engine which will severely enrich it. If the computer doesn't know this is happening the fuel mixture won't be right and it will not run well."

Replacing the valve seemed to resolve the issue for the Caddy guys...guess I'll give it a try this weekend.

Re: Code P0455 and the Gas Cap
 

Simple to test, unplug the electrical connector on the purge valve then disconnect evap line from cannister at purge valve with engine running and check for vacume at purge valve connector. If vacume is present valve is stuck open as it is a normally closed valve.

Re: Code P0455 and the Gas Cap
 

I apologize for hijacking a thread but I have the same codes and when I start my Hummer I get a extremely loud hissing sound for several seconds then it goes away. If I turn off the heat or AC, the hissing immediately stops. Any idea what this may be? I see you guys are talking about a "purge valve" and was wondering if that may be whats causing my problem?

Re: Code P0455 and the Gas Cap
 

I don't have a hiss...just trouble getting started after a gas-up. I've already replaced the 'usual suspects' (gas cap, evap solenoid)...I'm gonna do the purge valve tomorrow and see if that fixes anything.

Re: Code P0455 and the Gas Cap
 

Im confused as to why you wouldnt test it before replacing parts.

Re: Code P0455 and the Gas Cap
 

That's what I'm doing today. I'm fairly certain that it will react as you described.

Re: Code P0455 and the Gas Cap
 

Yep...the valve was stuck open. I slapped the new one on and cleared the codes. We'll see how it goes.