Hey I’m new here, and new-ish to doing my own automotive work. Ive owned my Colorado for about 5 years now and I’m at 195,021 miles. Love this truck. I use it for my pool service business & I’m hoping to keep using it for years & years. I was never a “car guy,” but I inherited a bunch of tools and the past 3 mechanics I’ve paid half-assed me into trouble (bad tune up that left me having to replace spark plugs & coil packs, caliper pins on rear seized up after a change, etc) so after jumping in, I’m really enjoying just doing it myself! But now I’ve got something I’m not sure how to diagnose. P0455 & P0442 error codes. Started with the small leak, and the mechanic said to ignore it, but now there’s the large leak. In case it’s relevant: I’d had a cylinder 6 misfire that seafoam seems to have solved, but I’d already replaced the intake manifold gasket, and my former mechanic purged the soliniod (buddy of mine thought my difficulty starting after getting gas was a stuck purge valve, so mechanic said he replaced that. Is it possible I have debris from the charcoal canister in my fuel filter? I heard a “smoke test” should help, so I got a “AutoLine Pro EVAP High Volume Smoke Machine Leak Tester with Built-in Air Pump” off Amazon, so I’ll be looking into that… here’s some images of how the vehicle is doing, though the large leak code cleared itself after adding more seafoam:
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Poolguy
P0455 & P0442 on 2015 Colorado 3.6L, V6 LT
Hey I’m new here, and new-ish to doing my own automotive work. Ive owned my Colorado for about 5 years now and I’m at 195,021 miles. Love this truck. I use it for my pool service business & I’m hoping to keep using it for years & years. I was never a “car guy,” but I inherited a bunch of tools and the past 3 mechanics I’ve paid half-assed me into trouble (bad tune up that left me having to replace spark plugs & coil packs, caliper pins on rear seized up after a change, etc) so after jumping in, I’m really enjoying just doing it myself! But now I’ve got something I’m not sure how to diagnose. P0455 & P0442 error codes. Started with the small leak, and the mechanic said to ignore it, but now there’s the large leak. In case it’s relevant: I’d had a cylinder 6 misfire that seafoam seems to have solved, but I’d already replaced the intake manifold gasket, and my former mechanic purged the soliniod (buddy of mine thought my difficulty starting after getting gas was a stuck purge valve, so mechanic said he replaced that. Is it possible I have debris from the charcoal canister in my fuel filter? I heard a “smoke test” should help, so I got a “AutoLine Pro EVAP High Volume Smoke Machine Leak Tester with Built-in Air Pump” off Amazon, so I’ll be looking into that… here’s some images of how the vehicle is doing, though the large leak code cleared itself after adding more seafoam:
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Difficulty starting after a fill up is often a leaky purge valve. What happens is the purge valve gets stuck open when it is supposed to be closed with the engine off.. So as the tank fills, the air from the tank with lots of fuel vapor gets pushed into the intake, causing an over fueling condition when you try to restart the engine. If the truck is difficult to start after a fill up, that is my first inspection. I dont know where the purge valve is on your truck, but if you hook a line to the feed end and blow into it, you should feel no air pass through it with the engine off. (Dont draw air from the purge valve back into your person, that is bad. 
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The P0455 clearing itself, and the seafoam are probably not directly connected.
It not likely that charcoal bits from the canister are clogging your fuel filter. The fuel filter is in the tank, and the charcoal bits do not usually find their way upstream like that. Its more possible that the charcoal bits are clogging the purge valve sometimes. That would be from over filling the tank and have fuel get into the canister, then bits find their way into the purge system. Possible, but also not terribly likely.
Do you have trouble filling your tank at all? Like premature click off from the gas pump? I had that trouble with another vehicle because the canister had gotten flooded. That also resulted in a P0455 because the excess fuel and charcoal messed with the vent valve. I ended up solving that by deleting the canister entirely, but the root cause was that the previous owner had overfilled the tank, flooding the canister. Then in my experiments, I ended up doing it too.
Looking at your LTFT at idle, I am thinking you still have a vacuum leak somewhere. Should be +/- 5% and you are 13/20%
)The P0455 clearing itself, and the seafoam are probably not directly connected.
It not likely that charcoal bits from the canister are clogging your fuel filter. The fuel filter is in the tank, and the charcoal bits do not usually find their way upstream like that. Its more possible that the charcoal bits are clogging the purge valve sometimes. That would be from over filling the tank and have fuel get into the canister, then bits find their way into the purge system. Possible, but also not terribly likely.
Do you have trouble filling your tank at all? Like premature click off from the gas pump? I had that trouble with another vehicle because the canister had gotten flooded. That also resulted in a P0455 because the excess fuel and charcoal messed with the vent valve. I ended up solving that by deleting the canister entirely, but the root cause was that the previous owner had overfilled the tank, flooding the canister. Then in my experiments, I ended up doing it too.
Looking at your LTFT at idle, I am thinking you still have a vacuum leak somewhere. Should be +/- 5% and you are 13/20%
hey, thanks for replying! I’m not sure how to tell if I’m overfilling, but the there’s no premature click when I’m adding fuel. I can say that when I do fill up, my gauge shows that it’s full for quite a while before the needle starts to come back down. Did removing the canister interfere with your vehicle’s computer and throw a bunch of codes???
OK, sounds like your venting system is operating OK, at least the vent isnt clogged or slow flow. But i do not have a good explanation for why the truck has a hard time starting after a fill up. Does it stumble every time you fill the tank?
If you stop when the gas pump clicks off, and dont try to "top it off" then most likely you are good there.
So removing the canister is totally transparent to my computer. On the 2008 Malibu i did it on, there is a main vent line coming off of the fuel pump that runs to the canister, and a smaller line that vents to the filler neck and main vent line with a T.
Off of the canister is the vent line to the vent valve, and the smaller line that goes to the purge valve. In my case, since the canister was bad, and expensive, I just replumbed the main vent line direct to the vent valve. And on the smaller line, the run that went from the T to the main vent line now just runs direct to the purge valve. So the purge system still operates to burn off vapors in the tank. The old car is a bit quirky, and I dont know why. above 2/3 of a tank I intermittently get a P0455. Below that, it goes away. Ive only had it this way for a month or so, but its working.
Even if I were in an inspection state, which I am not, it would pass inspection based on operation. The car doesn't understand the canister is gone. I am however, committing an environmental foul allowing vapors to vent without passing through the charcoal. I have not noticed any gas smell at all BTW.
Not recommending it, lol, but it can be done.
The EVAP codes do not really have any impact on your engine performance though. Unless the evap system is the source of a vacuum leak, via the purge valve. Then that can be trouble that behaves like a regular vacuum leak, and the occasional hard start after fill up. You are not getting any lean codes, so the problem isnt enough to make the computer mad at this time.
You can disconnect the purge valve from the intake and cap the intake port, and see how the truck runs then. You will likely get evap codes from that, but real performance will not be impacted. That would determine if the purge valve is the culprit for your symptoms. I dont have a gen 2 truck, so I dont know how the plumbing works on your particular vehicle, but in general what I described is how the systems operate. the coloradofans.com forum is the knowledge center for the gen 2 trucks.
If you stop when the gas pump clicks off, and dont try to "top it off" then most likely you are good there.
So removing the canister is totally transparent to my computer. On the 2008 Malibu i did it on, there is a main vent line coming off of the fuel pump that runs to the canister, and a smaller line that vents to the filler neck and main vent line with a T.
Off of the canister is the vent line to the vent valve, and the smaller line that goes to the purge valve. In my case, since the canister was bad, and expensive, I just replumbed the main vent line direct to the vent valve. And on the smaller line, the run that went from the T to the main vent line now just runs direct to the purge valve. So the purge system still operates to burn off vapors in the tank. The old car is a bit quirky, and I dont know why. above 2/3 of a tank I intermittently get a P0455. Below that, it goes away. Ive only had it this way for a month or so, but its working.
Even if I were in an inspection state, which I am not, it would pass inspection based on operation. The car doesn't understand the canister is gone. I am however, committing an environmental foul allowing vapors to vent without passing through the charcoal. I have not noticed any gas smell at all BTW.
Not recommending it, lol, but it can be done.
The EVAP codes do not really have any impact on your engine performance though. Unless the evap system is the source of a vacuum leak, via the purge valve. Then that can be trouble that behaves like a regular vacuum leak, and the occasional hard start after fill up. You are not getting any lean codes, so the problem isnt enough to make the computer mad at this time.
You can disconnect the purge valve from the intake and cap the intake port, and see how the truck runs then. You will likely get evap codes from that, but real performance will not be impacted. That would determine if the purge valve is the culprit for your symptoms. I dont have a gen 2 truck, so I dont know how the plumbing works on your particular vehicle, but in general what I described is how the systems operate. the coloradofans.com forum is the knowledge center for the gen 2 trucks.
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