2005 Suburban Z71 with a 5.3. The code is Evap large leak detected. Reasonably sure it is not the gas cap. I replaced it with a brand new AC Delco part, because the rubber was showing some signs of wear. The code is on its way back (has not set the check engine light, but has put a message in the information center to check gas cap). I've looked at all the rubber tubing I can see easily in the vicinity of the rear axle and filler neck from underneath. I do not see anything amiss. There are no other codes set or pending.
P0455 Code, where to look?
- Thread starter strad
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Erickk120
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Do you get pressure build up after parking from a trip and taking the gas cap off? Do you smell fuel gas in the air after driving it and coming out of it? I had the same exact symptoms as yours at the beginning with no check engine light, replaced the gas cap with a AC DELCO one, to no avail, I would get it triggered every time the weather was chilly, but eventually I got it every day and later I developed the other 2 symptoms I posted the start of this response and a check engine light, I noticed my charcoal canister was covered in transfer case oil, and I had replaced the vent and purge solenoid with aftermarket ones previously, that didn't help, I didn't take the time to diagnose the problem thoroughly but pulled the trigger and replaced the charcoal canister and both vent and purge solenoids with AC Delco ones, that fixed all the symptoms and got rid of the large leak code and check engine light. Most of the time if the lines are fine it just ends up being the purge valve.
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Have not noticed any fuel smell, and not much if any pressure at cap. I knew where the purge valve was located but didn't know where the charcoal canister was located. But you said yours got covered in transfer case oil so it has to be nearby! I'll take a look in there. I guess the purge valve likes to stick open which vents it constantly.
Erickk120
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When it comes to EVAP problems they can be hard to diagnose, especially if you don't have things like a smoke machine or one of those expensive computers, so I've always replaced the inexpensive things first before getting into the more expensive ones, that or get it diagnosed for 100-150 at a shop, I replaced the canister and both vent and purge since it was about the same anyways, and I knew my lines were fine and weren't leaking or cracked. Some people don't mind having the annoying chime every time they get in their truck, or the check engine light, but I my self hate seeing anything in the dash light up. I hope it is just one of the solenoids and not the canister, or something like a line.
easiest fix is to drop two bills and replace the hole shebang, (canister, 2 solenoids) or less depending on what manufacture you go with.
Well LOL. Last Sunday I replaced the vapor canister vent valve (with a BWD part). It took until Thurs with it being driven 60 miles a day for it to complete a drive cycle. And when it did, it threw a DIFFERENT code!! P0496. So I got a purge valve straight from the dealer (3 dollars less than the parts store lol). Prior to pulling the old one, I pulled the electrical connector off and the hose connection, started it up and sure enough I had some vacuum. Installed the new part and no more vacuum at start up. But seriously, what a PITA! It's like the whole system has decided to go on strike! I did not see any chunks of charcoal anywhere (was told to look for that) so I'm assuming at this point that I have no leaks (because I got a P496) and I know the purge valve was bad (because I had vacuum with it unplugged). So now I'm wondering what will happen next!
oldchev
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Glad you got that fixed. Observing your first post and answering the last you said you charcoal canister is covered with transfer case oil.
That should be next. Your transfer case should be dry outside unless you left your fill plug out or you have a seal leak.
That should be next. Your transfer case should be dry outside unless you left your fill plug out or you have a seal leak.
Actually that was one of the responders. I did actually have an issue with my transfer case "burping". But now that it has new fluid in it, that is no longer happening. And it didn't get on the charcoal canister in my case, only on the gas tank bottom.
I'm happy to report that it has now completed a drive cycle, and everybody's happy! No codes. So new purge and vent valves solved the problem. I'm just surprised they failed at nearly the same time.
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