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This is the closest I've come to a slightly different PO449 problem so I'm wondering if anyone reading this can provide an answer...
Everything running fine before GM initiated emissions recall requiring a software 'update' [#14535:Carbon Monoxide Emissions Mar 3, 2015 - Document ID: 4093968] Soon after, the Check Engine light came on (and stayed on) and the engine began idling rough so I returned it to the dealer who told me (sitting down?) that the solution now was to replace the timing chain. 88 minutes and one timing chain later (you can replace a 2.4L timing chain in under 2 hours - really?) I once again left the dealership confident that the issue had been resolved but after only a few miles couldn't help noticing that, although it seemed to be a bit running smoother, the CE light was still on. This time I was told that the software updates sometimes fail and they'd take another crack at it at my convenience.

Long story short - after a second emissions software update the CE light was still on and when they finally checked with the computer - sure enough: code PO449 = evap vent solenoid failure. Warned of an estimated $99 bill for a smoke test, I grabbed some tools, crawled under and investigated and guess what - the solenoid is just fine (looks and works like new) and there are NO cracks or loose vacuum fittings in the vacuum line (90% of the run from the engine back to the canister is a shiny metal pipe that for all the world looks to be aluminum or stainless steel with no sign of corrosion whatsoever). Soooo... unless it's somehow related to the emissions software update I'm totally stumped.
Any ideas?
 

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This is the closest I've come to a slightly different PO449 problem so I'm wondering if anyone reading this can provide an answer...
Everything running fine before GM initiated emissions recall requiring a software 'update' [#14535:Carbon Monoxide Emissions Mar 3, 2015 - Document ID: 4093968] Soon after, the Check Engine light came on (and stayed on) and the engine began idling rough so I returned it to the dealer who told me (sitting down?) that the solution now was to replace the timing chain. 88 minutes and one timing chain later (you can replace a 2.4L timing chain in under 2 hours - really?) I once again left the dealership confident that the issue had been resolved but after only a few miles couldn't help noticing that, although it seemed to be a bit running smoother, the CE light was still on. This time I was told that the software updates sometimes fail and they'd take another crack at it at my convenience.

Long story short - after a second emissions software update the CE light was still on and when they finally checked with the computer - sure enough: code PO449 = evap vent solenoid failure. Warned of an estimated $99 bill for a smoke test, I grabbed some tools, crawled under and investigated and guess what - the solenoid is just fine (looks and works like new) and there are NO cracks or loose vacuum fittings in the vacuum line (90% of the run from the engine back to the canister is a shiny metal pipe that for all the world looks to be aluminum or stainless steel with no sign of corrosion whatsoever). Soooo... unless it's somehow related to the emissions software update I'm totally stumped.
Any ideas?
To get help with your problem post your vehicle in the proper forum. list what you own,miles,engine,and other info about your vehicle including testing and driving issues.
 

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Also check the gas cap.

Ted
 

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I have a 2007 Silverado Classic 1500 Ext Cab 4x4 LT1. with a P0449 code according to a borrowed reader from Auto Zone. While I'm handy with building things and home renovations, my experience under the hood is minimal except for changing filters and oil. From the repair descriptions I've read however, this appears to be something I can do, rather than pay my neighborhood Firestone $434 ($344 + $90 to verify that the code is actually P0449. Firestone wanted $219 for the valve part alone, not including the canister, new hose if needed, or clamps).

In another forum article, it was stated that the Evac Cannister Purge Valve was located in "front" of the gas tank on the passenger side. Last night, I wiggled under truck....could not see the valve on the right or left side. In fact, there's nothing even resembling the value on either side all the way from the differential up to the transmission. Is it under the spare tire??? Or, between the spare and the gas tank???

Last question:
A part site, GMWholesaleDirect.com shows a schematic of the parts, but the valve (214-1680) doesn't look anyting like the schematic.

Amazon, they show ACDelco 214-2149 as the "incorrect" part this truck, however 200 reviews say that it is the correct part and GM made change mid-year. Amazon says the correct part is 214-2082, however reviewers said that part is incorrect.

AutoZone, which I would prefer (only because its close to my house) has 214-2149, an says it's the wrong part. They also have 214-1680, which looks like the GMWholesaleDirect part photo and they say it's the correct part, however Amazon says 214-1680 is not correct.

I have 1 vehicle, so I can't take it apart and go to the store or dealer with the bad part in hand looking for a match. How do I know which part is the correct one???
 

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I read every thread I could find on this subject and to start with every time I searched for the code P0455 I got a result for code P0449 . Confusing from the start. Then I tried everything everyone recommended ; change both the solenoids change the tubing, etc.with a ridiculous 38 bucks for a new fucking gas cap . The tube running across the top of the engine to the solenoid near the front of the block was broken at the connector on the other end where it descends near the firewall. This connection is inconveniently tucked away where it is so hard to get at you would have to think some kind of idiot designed it. Or someone wants to force you to pay a dealer for repairs.
Fixed that still got the code P0455.

So I bit the bullet and went to the dealer for the smoke test and I felt so ripped off because any responsible mechanic would've known from the get-go there was no need to do the smoke test if he had done this kind of work before. He could've diagnosed the problem immediately because there was a stench of gasoline everywhere within 10 feet of this truck and drops of oily gasoline on the floor.

But they had to make it worth their while and hose me for $150. I hope I can save you that expense and tell you that if all the other things don't work the problem will be your sending unit a.k.a. your fuel pump .
The dealership advised me they would have to lower the fuel tank to replace the unit and the cost would be around $1400.

I Took it over to my buddies where we undid the eight bolts that hold the box on then disconnected wiring to the tail lights and took off three screws in the filler neck. Lifted the box off. There before us was the top of the sending unit with three terribly corroded connections and little jet streams of a gas spewing in several directions. For such an important component to be so cheaply made on a truck less than seven years old is extremely disappointing.
I ran over to a local parts store and got the replacement for $440 installed it and everything has been fine ever since.

This all together took us about four hours, and I saved about $1000. I think if other members here find the same problem GM should be covering the cost of this vital component being replaced .
 

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Discussion Starter #26
Well after many years of no po449 codes its Back!!! With 170k now. And im due for state inspection this month but im going away for 2 weeks Sunday. So I will check the hose by the tank tonight and the gas cap. Updates soon...
 

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Discussion Starter #28
Adp-adapter. Anyway a update after I got side swipped in the parking lot where I work I got the 0449 code and service my four wheel drive. I changed my evap and the front 4wd actuator. And then used a snap on scanner to reset everything. And the code is still there and I can't switch into 4wd so the body shop is going to look at it. The bcm might have been hit. I will know this week..
 

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The auto parts stores will read codes and clear them for free. I would write them down so I could compare them if any came back. Are you pretty sure you fixed the problem?

Ted
 

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Sometimes trouble codes are set deeply into the PCM's memory, so do the necessary repair, if needed, then, after cancelling the code, open the hood, and locate the fuse for the PCM.
It is usually a 20 amp fuse, and with the ignition turned off, carefully pull the fuse out, then turn the key position to on, but don't crank the engine, next, turn the switch back to off, replace the fuse, and the code should be cleared from the vehicles PCM memory.

A Cadillac technician advised Me on this procedure some years back, and I hope that it works out for You as well.
 

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I have also had a gas cap light come on and i put a new gas cap but still having the check engine light come on and now having some issues when starting my truck. Can this same problem keep truck from starting right away? Or am i looking at a bigger problem?
 

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gas cap code is most times a leak like a cracked gas vapor canister or a vent vapor valve .. or you did not put the cap on ..

engine does not start good well that can be fuel pressure .. post a new post that is about your vehicle ,, reveal what your truck is yr/model/engine/drivetrain /miles/how long you owned it etc.. also you do the work ?
 
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