P0455 Chevrolet Code - Evaporative Emission System Large Leak Detected

Great thank you !!!

po455 code found problem gas cap not tighten.

checked the fuel cap & yes it was barely on put on, wife hates pumping gas. it on tight and disconnected the battery will have to wait the 30mins like suggested to see if the check engine light is reset.

Just had this code tonight (Advanced Auto Parts scanned my 2009 Avalanche's computer, for free). Did an Internet search and found your site. Fuel door was on, but cap appeared loose...clicked, but I could pull it right off with minimal force. Here's hoping this does the trick (traveling a few hours from home).

Found this code to be real common with 2006+ Impalas. If the gas cap is ruled out, then most like culprit is the fuel vent solenoid, located just behind the rear wheel well on the driver's side. They have a tendency to stick (Not operate), and get very dirty. The temporary fix can be to pull the assembly out (one 10mm bolt and a slip-fit hose connection), take it apart as much as you can (the top of the canister just snaps off, and the solenoid can come off with a twist) and clean the dirt out. I have used the garden hose to wash these, as they are just plastic. Clean the solenoid ports out carefully with LOW compressed air, as you do not want the rubber seal to come dis lodged. Assemble and try.
The permanent fix is to replace the entire unit. For older models (2006 to around 2012) there is a re-design to help fix the dirt sticking issue, however, you may need to get a "pigtail" converter for the electrical connector as well, as the new style has a different electrical connector.

Thanks for the information!!

I have a question on a p0455 code. I have replaced both solenoids, the charcoal canister and the gas cap. We did the smoke test and found no leaks. What else could be the culprit? The only thing I can think of is to disconnect and blow out the lines with air. I haven't done this yet. Any other ideas? Thanks

Clogged lines shouldn't cause that problem. Either there is a leak or the sensor and measures the pressure is not working properly. What model and year is your Chevrolet? I need to know to check the service manual

2004 Chevrolet Trailblazer LS, 4.2, auto , 4wd. Something else I noticed is that when I reset the computer I went 250 miles of freeway driving with no problems. When I was driving in town the next day is when the code came back up during stop and go driving, not going as fast. Is there something other that the purge solenoid that measures pressure? We had the vehicle on a hoist during the smoke test so we could monitor the tank and hoses for leaks. The system was hooked up at the time to put the system into active mode. Hope this helps, thanks.

Found 2 factory service bulletin that may help you diagnose the problem:

Second one, this one could be the problem:

I've never had a problem with the vehicle starting. When we did the smoke test it passed with no leaks at all. However we didn't try to move the filler neck by hand. This could be what we're missing. I'll set up another test and keep you informed, thanks.

question i just got the code on my 05 equinox changes canister purge valve and my issue is car will not start but once every 12 to 14 hours and once warm will not start back up something is making me think fuel pump any help would be appricated

Unfortunately there are several thing that could cause the no start situation, but the canister or anything related with the EVAP system shouldn't cause the no start situation. As you mention, the fuel pump could be the cause of the no start situation. Before replacing any parts check the fuel before you start the engine.

I have an 05 impala and have been having issues with it, the evap emission control is what popped up on the computer... but the other day while driving it went through a stop sign on its own. We had come to a complete stop, with the brakes pressed completely to the floor, and the engine was kind of running high... then next thing ya know the car just starts rolling right through the stop! With the brakes floored!! Anyone ever heard of anything like this happening? And it doesn't do it all the time, it drives fine for the most part, but acts up from time to time. I've had it in the shop but they can't diagnose what's wrong with it when it won't act up for them ): I'm at a loss for what to do and it's the only vehicle to get me and my children to and from. Thanks in advance!

If has nothing to do with eh P0455 code. The problem with the brakes, you could start by checking for brake fluid leak at the brake master cylinder of the brake calipers at the wheels.

Hello I have a 2005 Chevy Tahoe Z71. I am having issues putting gas it only takes a little gas at a time. I replaced the Canister and Purge Selenoid and I am still having an issue putting gas. Now I have codes P0446 and P0455 showing. Help please!

You could have a problem with EVAP Canister Vent Control Valve. This video may help you diagnose the problem.

https://www.youtube.com/wat...

Hello Doug,
I have a 2001 Tahoe with exactly ALL the problems you outlined! I'm doing a smoke test tomorrow, but was interested if you ever found a solution to your problem.

Thanks,
Michael

I have an '03 Chevy Impala LS ... had the analyzer hooked up and said an EVAP Leak ... mechanic said to try a new Gas Cap. Needless to say, the old cap needed replaced and now my car really takes off. However, the engine light still comes on.. How do you clear the engine code? Thanks much!!

The problem your having with the not being able to fill up is the vent valve, I had that problem and fixed it, but I'm waiting to see if that's the cause of the p0455, I got rid of the p0446 by dropping the tank and changing the ftps (fuel tank pressure sensor).

Have 2012 impala 3.6 changed both front valve and canister plus new gas cap still getting code p0455. About 3-4 days after reset codes

The P0455 code is for a major EVAP system leak. A hose must be broken or disconnected. Visual check all the hoses and components, if you can't find anything, then the next step is to check use a smog machine to find the leak.

wrong! My System was smoke tested! No hose leak. You realize that LARGE is not really large right? ..and small is a pinhole!

What a D-bag. You are an incoherent tool. OBDII tech was only offering help based off of the codes.

I have an 07 tahoe, 5.3. I got the "tighten gas cap" message on my dash, followed by a check engine light. I've had the truck 3 years and it's always been hard to pump gas. So when I got the light I changed the vent solenoid above the spare tire. Cleared out the codes and it was good. Went to put gas in, no problem. Then a few days later the check engine light came back. Checked the code, PO455 large leak. I cleared it and it came back the next day. Also it started being difficult to pump gas again. Could the solenoid be bad? I got it from rockauto.com. I just order a new gas cap, waiting for it to come in.

I have a 2003 Chevy Tahoe Z71. got an engine light on with the code P0455. Gas cap was on tight, when I opened it I got a face full of pressure release. Engine runs fine and no power loss. Is it safe to drive in this condition?

Yes. It's safe to drive. Just make sure the cap is tight and then clear the code.
If the code comes back, then you may have to a shop further diagnose the problem. You could have a loose or cracked EVAP system hose.

I have a 2005 Avalanche 1500. Same problem as Doug p0455. replaced the vent solenoid, replaced the purge solenoid, I even went as far as running a new signal wire from the computer module to the vent solenoid. Removes the purge solenoid to check the o-ring and re-installed it making sure it was seated properly. I used a teat lamp to check the computer driver and it seems to be working, the lamp comes on nice and bright so that tells me that there is enough current to power the solenoid. The only thing that's stopping me from buying a new computer module is the p0455 is a large leak error not a circuit error. Did a smoke check no leaks. changed the gas cap. One thing I did do just for giggles and grins. I tapped in to the white signal wire so I could bypass the computer driver. and connected it to ground to activate the solenoid (we all now the white signal wire that goes to the computer is connected to a transistor that pulls ground.) any way I would connect that to ground before I would start driving and I would not get the loos gas cap message or the engine light.
I could drive for days that way. with now error. But as soon as I disconnected the ground bypass the gas cap message and engine light would come back.