4 replies to this topic

[vaughncurtis38]

On my 2003 Chevrolet Silverado the CEL is on when i used the obd2 scanner I got these codes:

-P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
-P0455 Evaporative Emission Control System Leak Detected (gross leak)

Where should I start to try to fix this I have read and studied for a while even changed the purge valve and reset it but it came back on . Thanks in Advance.

[95Sierra2500]

If the purge valve didn't fix it, it could be your carbon canister having an issue (broken/clogged). But I'd actually consider checking your gas cap. Make sure you put it on at least 3 clicks past where it stops, or you'll get these types of codes. 9 times out of 10, it's the gas cap. If simply unscrewing it and tightening it, then clearing the codes doesn't fix it, try replacing the cap.

[sparkstech]

If the purge valve didn't fix it, it could be your carbon canister having an issue (broken/clogged). But I'd actually consider checking your gas cap. Make sure you put it on at least 3 clicks past where it stops, or you'll get these types of codes. 9 times out of 10, it's the gas cap. If simply unscrewing it and tightening it, then clearing the codes doesn't fix it, try replacing the cap.

I don't mean to bust on ya but are you a tech because this is bad advice and a waste of money. The p0455 is for a leak concern and if that was the only code I'd say give the cap a shot. However the p0455 is most likely just a side effect of the P0449. The P0449 is a test that is run on the vent solenoid circuit to check the electrical functions in basic terms. The computer is putting out voltage amount X and in a properly functioning circuit it knows it will see voltage amount Y come back. It isn't coming back as what it expects to come back at so there must be something electrically wrong with the vent circuit. And of course if the vent doesn't work you get a large leak. If we are just throwing parts at trucks the logical one for you is a vent valve. There is an updated part and a bulliten, I can't post them but do a simple search here and you'll find it. I say it's the most likely but don't get mad at me if it's not the problem. The vent circuit is powered full time by the 4ws fuse in the underhood fuse block and you can check for power all the way up to the valve. Unfortunately without a scan tool that can control the vent circuit thats about all you can check. The PCM grounds the circuit when necessary so unless you can make the pcm command it you can't really check the ground circuit.

[Indy]

TSB 04-06-04-055a
vent solenoid 10382105 I believe. I've been driving around with PO449 and PO452 for 5 years plus. I check the codes every week or two because once the CEL is on, it's on and you don't know if new codes have appeared.

[blinddc388]

If the purge valve didn't fix it, it could be your carbon canister having an issue (broken/clogged). But I'd actually consider checking your gas cap. Make sure you put it on at least 3 clicks past where it stops, or you'll get these types of codes. 9 times out of 10, it's the gas cap. If simply unscrewing it and tightening it, then clearing the codes doesn't fix it, try replacing the cap.

I don't mean to bust on ya but are you a tech because this is bad advice and a waste of money. The p0455 is for a leak concern and if that was the only code I'd say give the cap a shot. However the p0455 is most likely just a side effect of the P0449. The P0449 is a test that is run on the vent solenoid circuit to check the electrical functions in basic terms. The computer is putting out voltage amount X and in a properly functioning circuit it knows it will see voltage amount Y come back. It isn't coming back as what it expects to come back at so there must be something electrically wrong with the vent circuit. And of course if the vent doesn't work you get a large leak. If we are just throwing parts at trucks the logical one for you is a vent valve. There is an updated part and a bulliten, I can't post them but do a simple search here and you'll find it. I say it's the most likely but don't get mad at me if it's not the problem. The vent circuit is powered full time by the 4ws fuse in the underhood fuse block and you can check for power all the way up to the valve. Unfortunately without a scan tool that can control the vent circuit thats about all you can check. The PCM grounds the circuit when necessary so unless you can make the pcm command it you can't really check the ground circuit.

Im having the same problem on my 2005 GMC2500. Im only getting a P0445 not a P0449.
And your currect when saying a fuel cap is a waste of money because it hasent fixed my problem. (I figured it wouldn't work but for 5 bucks its worth a shot). I worked on a car last week with the same problem and it turned out to be a vaccum line going to the EGR valve. I checked it on my tuck and replaced it, after finding a few cracks around the ends. I cleared the code and it came back. Any clue on what step i should take next? Any starting point would help me.