p0449 - Chevy Colorado & GMC Canyon
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post #1 of 91 (permalink) Old 04-06-2009, 09:18 AM Thread Starter
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p0449

fault code p0449. Already replaced the vent solenoid, verified the solenoid does indeed work, have power at the solenoid but the ground never closes. I know this because I cleared the code and laid underneith the truck with a test light hooked up and waited for the code to show up again.. which it did but the light never lit.. and the light does work. The wiring itself looks fine as far as I could see. So now what is the next step. Is there a relay or something that tells the ground to close... and if so where is it.
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post #2 of 91 (permalink) Old 04-06-2009, 01:56 PM
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Re: p0449

this should help in understanding the evap system.
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post #3 of 91 (permalink) Old 04-06-2009, 02:48 PM Thread Starter
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Re: p0449

Thanks!! it was actually the canister purge valve I replaced.. I'll have to have a look at the vent and see if it is also bad. Just as note if you ever have to replace the canister purge valve it is around $200 but the Hummer H2 has the identical part and it sells for $45.. the only difference is the H2 one doesn't come with a new pipe.. it took me about 14 seconds to pull the old pipe off and re-use it so I figured it was worth the $150 savings.
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post #4 of 91 (permalink) Old 04-06-2009, 07:38 PM Thread Starter
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Re: p0449

tonight I took off the purge valve tonight and jumped it and it opened up fine.. power to the valve but it never gets the command to open. So now both purge valve and vent valve have been confirmed to work and power is going to both valves so I guess that leaves me with the ground not being closed... which I am now lead to believe is a problem with the pcm. Any thoughts/suggestions.. any way to test the pcm
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post #5 of 91 (permalink) Old 04-06-2009, 08:02 PM
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Re: p0449

yes the pcm grounds the solinoids.
need a scan tool to check/force the evap to test itself with the pcm.
but on turning the key on for startup it should run its own self test????
same as many ppl get the loose gas cap code/light.
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post #6 of 91 (permalink) Old 04-06-2009, 08:58 PM
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Re: p0449

Quote:
Originally Posted by nateashfield
tonight I took off the purge valve tonight and jumped it and it opened up fine.. power to the valve but it never gets the command to open. So now both purge valve and vent valve have been confirmed to work and power is going to both valves so I guess that leaves me with the ground not being closed... which I am now lead to believe is a problem with the pcm. Any thoughts/suggestions.. any way to test the pcm
I've been looking over the info that mazdab2600 posted. I would agree that the pcm supplies the ground. You said both the vent solenoid and purge solenoid are getting power.
So after reading up on exactly how the system works, I came up with some possible answers. When the engine is cold and first started the pcm sends a ground to the purge valve so it opens but not the vent solenoid so it stays closed. This creates a vacuum from the throttle body all the way back to the canister. The pcm then closes the purge valve, trapping the vacuum and monitors the fuel pressure sensor. If pressure starts dropping, the pcm thinks it has detected a leak and will set a code.

Once the engine is warmed up, the pcm opens the vent valve and based on signals from the fuel pressure sensor, it opens and closes the purge valve as needed to let the vapors pass to the throttlebody. So here's my suggestions: Carefully inspect the evap tubing from the throttle body to the purge valve and from the purge valve back to the canister for any kind of breaks or even hairline cracks. Once you verify all the tubing is okay, I would suspect the fuel pressure sensor or wiring to it is the cause.

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post #7 of 91 (permalink) Old 04-06-2009, 09:09 PM Thread Starter
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Re: p0449

well I guess in the morning I'll try to pressurize the system through the test port and spray all the lines and connectors with some soapy water and see what happens.. What will actually set the P0449 code?
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post #8 of 91 (permalink) Old 04-06-2009, 09:32 PM
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Re: p0449

just googgled the 0449 code.
found this check for a fuse marked-CNSTR VENT see if its blown???

http://355nation.net/forum/engine-drive ... p0449.html


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post #9 of 91 (permalink) Old 04-06-2009, 09:50 PM
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Re: p0449

Quote:
Originally Posted by nateashfield
well I guess in the morning I'll try to pressurize the system through the test port and spray all the lines and connectors with some soapy water and see what happens.. What will actually set the P0449 code?
A loose or defective gas cap, a vacuum leak in the system, a defective fuel pressure sensor, or the pcm isn't getting a signal from the sensor.

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post #10 of 91 (permalink) Old 04-06-2009, 10:26 PM
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Re: p0449

I just got the same code last week. It usually starts as a gas cap message on the dash and eventually lights the check engine light. I have cleared it twice and it keeps coming back about 5 minutes into driving. I planned to get a new gas cap but I do no think that is the problem. the truck only has 60k and most of that is highway, Relatively speaking that gas cap has not had many cycles of use....

I am curious how this turns out for you. I think I need an emissions test this summer for plates and need to get rid of that light.

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post #11 of 91 (permalink) Old 04-07-2009, 03:44 PM Thread Starter
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Re: p0449

looks like I'm off to the dealer tommorrow . both valves work, wiring is good, no leaks, purge valve is getting the signal and is functioning .. still don't seem to be getting the signal for the vent valve to close so the only thing that is left as far as i can see is the pcm. Gonna get it hooked up to the tech II tommorrow and try to force the command for the vent valve to close.. if it doesn't then I guess I'm out $600 for a new pcm.
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post #12 of 91 (permalink) Old 04-07-2009, 05:21 PM
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Re: p0449

Keep us posted.

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post #13 of 91 (permalink) Old 04-08-2009, 07:43 PM Thread Starter
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Re: p0449

Got the truck fixed today!! Actually discovered I had a friend that had a scan tool that could make commands. Went there today and hooked up the tool and comanded the vent to close and actually got the ground this time but the valve never moved so I went back to the valve to take it out and while I was unplugging the connector the valve closed.. Just a fluke.. Ended up being a loose connection in the plug.. The reason I never picked it up before was I was poking the voltmeter and test light into the socket so it was tight but when it was actually plugged into the valve it was loose. Took the plug apart and bent the prongs and problem solved. My friend the mechanic said that if the pcm commands the valve closed and there is a short or open circuit that it will stop the command so fast that a test light or even a voltmeter probably would not be quick enough to pick it up.. I guess thats where a scan tool comes in handy to command it closed and leave the command on. I'm pretty happy.. I was sure that I needed a new pcm but in the end it was just a new valve and a little bending.
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post #14 of 91 (permalink) Old 04-09-2009, 08:03 AM
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Re: p0449

Which valve had the loose connection? The one on the evap canister or on the side of the engine?

I need to check into mine this weekend.

Thanks for the updates,

Dan

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post #15 of 91 (permalink) Old 04-09-2009, 08:40 AM Thread Starter
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Re: p0449

the vent valve on the evap canister.. if you take the valve off .. you should be able to blow through it .. My orignal valve was stuck shut so I had to replace it.. like I said earlier.. if you have to replace it take it off and take it in and ask for a hummer one.. there about $150 cheaper and its the identical part... also you can hook it up directly to your battery and you should be able to hear it move.. Good luck
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post #16 of 91 (permalink) Old 04-16-2009, 11:27 PM
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Re: p0449

Sweet! I'm going to try this.
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post #17 of 91 (permalink) Old 04-17-2009, 05:47 PM
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Re: p0449

Hi:

I have a 2006, Z85 crew cab, 2wd.
I'm dealing with the same trouble code! the fantastic (P0449)
I call to the dealer to ask about the Emissions warranty, they told me that this only cover the catalytic converter no more than that so is not life-long, or else at least here in Puerto Rico.
So I try to fix it by myself and begin with changing the gas cap, to see what happened, but nothing happened.
I tried to test my valve canister out of the canister, put some direct DC from the battery, but it doesn't make any move or sound. I don't think the valve is shut up, because I can blow through it, the voltage at the rear end plug is present when I put on the key "on".

Do you think I have a bad valve?

Any suggestions about how I can test the valve again to be sure? At the beginning the code comes on and off now is all the time on!

Thanks

Victor

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post #18 of 91 (permalink) Old 04-17-2009, 08:14 PM
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Re: p0449

Victor - I am not trying to insult your intelligence. Make sure you have a ground wire connected to the solenoid valve when you apply power to it.

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post #19 of 91 (permalink) Old 04-17-2009, 10:09 PM Thread Starter
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Re: p0449

I would guess your valve is stuck open then. If you take it off and apply a ground and power from the battery and don't here it click and can still blow through it with power to it then it is stuck open and needs to be replaced. Good luck
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post #20 of 91 (permalink) Old 04-17-2009, 10:14 PM
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Re: p0449

Oh men!!

Thanks for the advice, but off course I connect the ground.
One lead for + and the other one, let me see? is only one left it has to be the (---). Je,Je,Je, was a joke. :P

By the way I'm electronic tech., that's why I'm almost sure it has to be bad.
The resistance that the multimeter gives from the solenoid me is very high, that's why I think that the coil of the solenoid is open.


Victor

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Rugged Bed Linner, Front Tinted Windows,
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Cooper S/T, 31x10.5xR15 Tires, 2'' Bubaloo Shackles, 2'' Front Strut Spacers.
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