Emissions Problem

voorheisb · December 15, 2009

Morning Everyone:

I have a 2003 Chevy Silverado 1500 Z71. I believe it is a 5.3L. I use another car since I commute a good distance so the truck only has around 40K miles.

Anyway, it failed emissions when I went to get my inspection sticker. It is throwing the following two codes:

PO449: "EVAP Control System Vent Valve Malfunction"

PO455: "EVAP Control System Leak"

I really can't spend a ton of money having the dealer troubleshoot and replace things unnecessarily. I'm hoping that someone here may have experienced the same thing or that this might possibly be somewhat common for this year truck. I've scoured the net for the last month but really didn't find anything conclusive.

Please let me know if any further information is required.

Any help would be greatly appreciated. I need it for the winter and it currently has a rejection sticker so I cannot legally drive it in Massachusetts.

Thanks,

Brian

Nytemare · December 15, 2009

Trust me...the dealership will not just randomly replace parts until its fixed...thats what you will do yourself. Everyone on here will have a different part for you to replace, and if you do all of them...you will have a new evap system by the time your done.

There is a thread here that has been written up very well explaining the evap system...I'll have a look for it and post it for you.

Having said all this...its probably the vent valve thats stuck, with some road grit or something.

Nytemare · December 15, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

voorheisb · December 15, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

Nytemare · December 15, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

Well....they have to diagnose the problem before they can tell you what it costs. But once diagnosed...they know exactly what to replace. Its cheaper to spend the 75..and the 2 hrs labor to get it done right than it is to keep guessing and replacing parts...that cost way more than what the dealership would have charged you.

I would tell you to take it to an independent shop...but nowadays, even independent shops charge 90+ bucks an hour...and since they don't work on one specific vehicle all day long...they are just guessing for the most part...all be it a much better guess than the average guy. But since they don't exactly know what the usual suspect is...it may take them 3 hrs where it would take the dealer 2...only thing a shop will save you on is the price on the part...as the GM replacements are way overpriced.

Just trying to save you some cash man....sometimes you have to bite the bullet and spend a few hundred bucks so you can save a few hundred.

desrtrat · December 15, 2009

also check to see if your still under federal emission warranty..i belive its 8yrs/80000 mi

good luck

minibike132 · December 16, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

It's not the canister, that would be a restriction not a leak. Well that isn't totally correct the canister could be cracked and leaking but those are far and few between so if you are looking for an experienced educated guess that wouldn't be it.

P0449 is a code that indicates an electrical malfunction with the vent valve. That would also explain the P0455. That isn't to say that you don't have more then one issue but it is most likely just the one. There is no way for you to check the ground side of the circuit but you can check for power to the vent valve, and if the power side is ok you can manually ground the other side of the valve and see if you can blow through it. If you have power and ground and the valve doesn't click you need a valve. If the valve clicks and you can blow through it you need a valve. If it tests good then there is an issue with the circuit and there is no way that I know of to test it the right way without a bi-directional scanner.

Nytemare · December 16, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

It's not the canister, that would be a restriction not a leak. Well that isn't totally correct the canister could be cracked and leaking but those are far and few between so if you are looking for an experienced educated guess that wouldn't be it.

P0449 is a code that indicates an electrical malfunction with the vent valve. That would also explain the P0455. That isn't to say that you don't have more then one issue but it is most likely just the one. There is no way for you to check the ground side of the circuit but you can check for power to the vent valve, and if the power side is ok you can manually ground the other side of the valve and see if you can blow through it. If you have power and ground and the valve doesn't click you need a valve. If the valve clicks and you can blow through it you need a valve. If it tests good then there is an issue with the circuit and there is no way that I know of to test it the right way without a bi-directional scanner.

That's the kind of experience and competence you get for 100+ bucks an hour....just wish you guys would get more out of that 100 bones.

That's why I say most of the time its better to go to the dealer with weird stuff going on...other than on parts cost...they will save you money as opposed to a general shop.'

minibike132 · December 16, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

It's not the canister, that would be a restriction not a leak. Well that isn't totally correct the canister could be cracked and leaking but those are far and few between so if you are looking for an experienced educated guess that wouldn't be it.

P0449 is a code that indicates an electrical malfunction with the vent valve. That would also explain the P0455. That isn't to say that you don't have more then one issue but it is most likely just the one. There is no way for you to check the ground side of the circuit but you can check for power to the vent valve, and if the power side is ok you can manually ground the other side of the valve and see if you can blow through it. If you have power and ground and the valve doesn't click you need a valve. If the valve clicks and you can blow through it you need a valve. If it tests good then there is an issue with the circuit and there is no way that I know of to test it the right way without a bi-directional scanner.

That's the kind of experience and competence you get for 100+ bucks an hour....just wish you guys would get more out of that 100 bones.

That's why I say most of the time its better to go to the dealer with weird stuff going on...other than on parts cost...they will save you money as opposed to a general shop.'

I wish the experience got me 100 an hour, half that would be great.

Nytemare · December 16, 2009

here ya go...its a very good writeup by a actual GM tech.

http://www.gm-trucks.com/forums/index.php?...569&hl=evap

I should have been more clear. I asked the dealership who said they couldn't even give me a rough estimate without putting it on the machine which costs $75. From what I had read before, I was leaning toward the charcoal canister. Again, thanks for your help. I really appreciate it.

- Brian

It's not the canister, that would be a restriction not a leak. Well that isn't totally correct the canister could be cracked and leaking but those are far and few between so if you are looking for an experienced educated guess that wouldn't be it.

P0449 is a code that indicates an electrical malfunction with the vent valve. That would also explain the P0455. That isn't to say that you don't have more then one issue but it is most likely just the one. There is no way for you to check the ground side of the circuit but you can check for power to the vent valve, and if the power side is ok you can manually ground the other side of the valve and see if you can blow through it. If you have power and ground and the valve doesn't click you need a valve. If the valve clicks and you can blow through it you need a valve. If it tests good then there is an issue with the circuit and there is no way that I know of to test it the right way without a bi-directional scanner.

That's the kind of experience and competence you get for 100+ bucks an hour....just wish you guys would get more out of that 100 bones.

That's why I say most of the time its better to go to the dealer with weird stuff going on...other than on parts cost...they will save you money as opposed to a general shop.'

I wish the experience got me 100 an hour, half that would be great.

No doubt man.

I think its BS...you guys should get at least 50% of the hourly rate...than split the other 50% up 30% between the writers, apprentices and Service managers, and 20% for the shop (GM). Its more like 50% for the shop now...and everyone else splits up the other 50%.