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Discussion Starter #1 (Edited)
2006 Impala 3LT - P0455 Large Evap Leak - FIXED!! see below

I have the P0455 Large Evap Leak code after I had been prompted to tighten my gas cap. I tried to tighten the cap... it would click 3x and then I could still pull it straight out.

So I thought "Ahhh ha!, I can fix this". Bought a new cap and it clicked on real tight and would not pull straight out. So I cleared the code and after 1 day, the tighten gas cap came on again. Then eventually the P0455 popped up again.

So almost every forum I've read says to bite the bullet and take it into a shop and have it 'smoked'. But I dont have the $95 for the shop to just "look" at it. So I was hoping to get some suggestions from any of you. So, I'm always opting to learn more from the field since that's where most of the action happens anyway.

Does anyone know where the charcoal canister is located? I found what I believe is the purge or vent valve behind the gas cap door (looking from underneath the left rear quarter panel). But if anyone else has had this similar problem with any tips to help me out, I'd greatly appreciate it. Many thanks!
 

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When this happened with my '06 a year ago, it was the evap solenoid. Now, a year after it was fixed at the dealer, I'm getting the "tighten gas cap" message and engine light again! :(
 

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When this happened with my '06 a year ago, it was the evap solenoid. Now, a year after it was fixed at the dealer, I'm getting the "tighten gas cap" message and engine light again! :(
I did hear about the solenoid issue before... also someone had a bad canister (cracked or something like that). I believe the solenoid valve is located behind the gas cap? I don't have a flow diagram, but maybe those valves are junk...especially if you were able to make it for a year with no problems?

Maybe I'll pull my valve and give a shot at bench testing it... it should be simple enough, but if there is any experience out there with tips, I'll gladly listen.
 

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Here is what the charcoal canister looks like,
http://www.parts.com/oemcatalog/index.cfm?action=getJointLocator&siteid=2&chapter=&Sectionids=0,2496&groupid=2497&subgroupid=2500&componentid=0&makeid=6&model=Impala&year=2006&graphicID=CB06280&callout=1&catalogid=2&displayCatalogid=0
Look at the number 1 item in the illustration, I think this part is in the engine compartment. Hope this helps. Kenny
Thanks Kenny, I also appreciate the lead on getting parts information with diagrams. Pretty cool.
 

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Discussion Starter #8 (Edited)
P0455 problem Fixed!

P0455 problem Fixed!

Well, after hearing some of the items my problem could have been, I finally took a look at the solenoid vent valve behind the gas cap. This is accessed from underneath the car, or more accessable, behind the plastic shrowd in the left rear well well. I was replacing brake pads and pulled a few clips and a screw to pull this back out of the way and the solenoid is right there.

First I disconnected the wire connector and it's a 12VDC 2-conductor (red/black) connector. I put a meter on it and turned the ignition over (not starting) to see if I got 12VDC. The computer cycles the solenoid upon start to initiate a leak check on the evap system. Well, I had the 12VDC I needed, so that eliminated half of the check. So, then I disconnected the actual valve from the bracket. The valve itself consists of two pieces. One is a filter housing and the other is the actual solenoid. You can actually disconnect the solenoid from the housing by lifting a plastic locking tab that locks the solenoid the the filter housing and then rotating the solenoid from the housing 90-degrees (1/4 turn connection), it will pull out. The nipple from the solenoid has a green o-ring on it.

Then I took a couple of wire leads I had made up and connected them to the battery just to see if the solenoid cycled. I don't think it really matters with a solenoid but you may want to be sure to connect the positive lead to the proper pin. You have to look at the connector on the car to verify which is red(+) and black(-), then apply to the proper pin at the solenoid itself. Like I said, I don't think DC voltage changes how the solenoid is energized, but just in case, follow suit with the power connector. It sounded like it was cycling very faintly, but also could be verifed by looking through the inlet of the solenoid and out of the outlet (you should be able to see into the inlet through the outlet when the solenoid is NOT excited.) Well, it was not cycling (could still see through). So I knocked the solenoid on a piece of wood a couple times gently and tried it again and then I could see the plunger opening and closing. So I thought it might had been just stuck. But after cycling it about 6-7 times it stopped cycling, but could then hear that faint clicking sound. So basically, it's junk.

These are solid state solenoids and can not really be repaired. So I went to the GM dealership and purchased one for $37. plugged it in... cleared the engine light and code by disconnecting the battery for 10-15 seconds (or you can use a code scanner to clear it). Started up the car and it's been a month or so since and I have no "Tighten Gas Cap" or Engine light codes.

So, apparently this valve was open all the time and was failing the vac check causing the engine light and Gas Cap messages... i.e. Large Evap Leak all the time causing horrible gas mileage.

I know this was pretty lengthy and detailed, but I hope it helps if you are also having this problem.

Please drop a reply if this DOES or DOES NOT fix your problem. I'd like to know. Thanks
 

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Glad to hear that your problem is now fixed. Though detailed it is very easy to follow.
 

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Thank you scusack!

I was having the same problem with my 2006 Impala SS. The tighten gas cap light was coming on and eventually the check engine light came on and logged a P0455 code. I followed scusack's post and tested my evap solenoid located near the fuel neck. I found that when I applied 12v the old one barely clicked as apposed to the new one that I could hear moving. I replaced the solenoid and cleared the codes tonight. Hopefully this solves the problem. Thanks again scusack.
 

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Hmm.. I might be able to apply this to the wife's '96 GA too. Been having a general "evap leak" or "vacuum leak" code popping up (P0440). The canister looks good but I never thought about a purge valve/solenoid. The car has had shitty mileage for a year or so and when you open up the gas cap (replaced that twice too) there's no pressure/hiss present at all. EVER.

Thanks guys!
 

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Hi cbmikey-
I subscribed to AllDatadiy.com yesterday, it cost $45 for 5 years. It had cheaper rates per year but I am hoping to keep my car for awhile. It provided me with all of the same troubleshooting charts/info that a shop would have used to troubleshoot the p0455. I did not really need it as a previous post from scusack solved my problem(Thanks again!), but it did have a lot of good info. I would send you the chart for a p0440 but it was not listed for my impala. You might want to check out that site. Hope this helps.

Thanks
Brett
 

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I know this is an old thread, but I am having P0440 pop up in one of our 02 impalas, is there any chance you could send me one of those charts?
 

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scusack, Thanks for posting your story, your problem was identical to mine. I just finished installing a new Solenoid Vent Valve and I'm hopeful that it will make the Check Engine light stay out. When I pulled the old valve I noticed that the plastic casing around the valve was bulged and cracked in two places and when I applied voltage directly to it nothing would happen.
In Canada the valve came as part of the attached canister, bracket and pipe so it cost me a little more at $95, but I was just happy they had it in stock. Now hopefully the light stays out so I can use the remote start function. Winter is coming and the remote start won't work if the Check Engine light is on.

Thanks again for taking the time to post your experience, I will update this thread if the new valve doesn't solve my problem.
 

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warranty on evap solenoid?

does any one know how long the evap solenoid is warrantied for? I replaced not quite a year ago and it's done again (po455) I checked the gas cap and it's tight and I changed that last year too. What a piece of junk that valve is.
 

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PO 455 Code

I have a 2007 chevy Impala and had the same issue. I bought a new cap and installed it & reset the code, however it returned. I read about the canister solenoid and took a chance, replacing it. I found a crack in the side plastic housing. I reset the code again and to date haven't had the code show up. Through a GM dealer it cost $73 for the replacement, probably get it a lot cheaper at autozone or someplace like that. It took about a 1/2 hour to change and is found in behind drivers side rear wheel next to gas filler tube.
So, thanks for heading me in the right direction & I hope this helps others.
 

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This is an extremly common problem for these cars. It's either the valve, as many of you know, or it's the gas filler tube has rotted, and has a hole. If you live in a salty place, (winter roads or coast) check that first. Sometimes you'll get a PO442 as well.
 

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Thank you so much!

I have a 2006 LT. I had the same problem with the large EVAP leak code and therefore could not remote start my car for a year. Luckily, I found your very detailed description of how you fixed it and I was able to fix it myself. I paid $32 for the part and not knowing anything about cars I was able to change it myself! The dealer and independent shops could not find anything wrong with my system and kept saying I would need a fog machine. I am so glad I did not pay for that. The engine light turned off and has stayed off for over a month! I really appreciate you taking the time to post your fix on here to save other people time and money.:icon_flower::icon_cheers:
 
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