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Discussion Starter #1
I know that this situation has been posted before in the forum but one really posted a fix or results of their fixes.

My 2008 Cobalt LT2 has been giving me the P0446 code for the last day or 2. I checked the purge valve by trying to blow air through it using my mouth but nothing would go through (unhooked completely) Then i looked at the canister under the car ran a bench test on the vent valve and it works fine opens and closes as its suppose to. theres a 3 prong hook up on the canister i dont know what that is alittle insight on that would be great. I blew light air through the vent pipe thinking there was a blockage. Is there anything else i should try before i start ripping parts?

THIS IS MY FIRST POST BUT IVE BEEN LOOKING AT YOUR FORUMS FOR A WHILE DECIDED ITS ABOUT TIME TO SIGN UP.:toung:
 

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My daughter just came home with the Cobalt and the check engine light was on. Same code I will work on this and let you know.

Conditions for Running the DTC
• DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0128, P0222, P0223, P0443, P0449, P0452, P0453, P0455, P0496, P0502, P0562, P0563 are not set.

• The ignition voltage is between 11-18 volts.

• The barometric pressure (BARO) is more than 68 kPa.

• The fuel level is between 15-85 percent.

• The estimated ambient air temperature is between 2-32°C (35.6-90°F).

• The start-up ECT and estimated ambient air temperature are within 9°C (16.2°F) of each other.

• The vehicle speed sensor (VSS) is less than 1.7 km/h (2 mph).

• The purge solenoid valve is enabled.

• DTC P0446 will attempt to run up to 10 times until it successfully completes.

• DTC P0446 completes one test per trip when the above conditions have been met.

Conditions for Setting the DTC
The fuel tank pressure (FTP) sensor is more than 3 inches H2O vacuum for 4 seconds during the 10 minute test.

Action Taken When the DTC Sets
DTC P0446 is a Type B DTC.

Conditions for Clearing the MIL/DTC
DTC P0446 is a Type B DTC.

Diagnostic Aids
• An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.

• An EVAP canister filter that is restricted can cause this DTC to set.
 

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Discussion Starter #3
Alright coby thanks

---------- Post added at 06:40 PM ---------- Previous post was at 06:09 PM ----------

The only other thing I can think of is my fuel tank pressure sensor but the only code is p0446 nothing else
 

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Well got the code (P0446) again finally today, so cleaning connectors and vent lines did nothing for me, although it's been almost 2 weeks since last CEL. so I purchased Vapor Canister Solenoid Valve today and will install it as soon as I can get my hands on the car.

 

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OK, pulled old evap solenoid out this morning. Once I unlocked it by turning counter clockwice 90° it practically fell out. After testing the old one and found it to work OK, I didn't think this was my problem but since I had already purchased a new decided to install the new one. This is when I realised that what the problem might be was leaking "O" rings. As the old one came out very loosely the new one needed pursuasion to insert into place. Now it's a waiting game to see if CEL is going to come on again.





---------- Post added at 01:57 PM ---------- Previous post was at 01:55 PM ----------

Not convinced that this will solve my problem with the P0446 code.
 

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Code's back. F&%/"
 

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Discussion Starter #8
Did you take the canister off the car. and shake it sometimes charcoal breaks loose. also take off your purge valve and clean that. if that doesnt work smoke test it
 

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Update. Yesterday, morning I changed the purge valve under the hood and cleared the code. I drove the car all day yesterday and my daughter has it today. It's a waiting game now but again doubth this is my problem since old purge valve seems to work fine on the workbench. Unless the "O" rings are wore out at the fitting.

This is the old purge valve.


Just have to pull on locking clip to remove from bracket.


---------- Post added at 11:07 AM ---------- Previous post was at 11:04 AM ----------

If this fails I will disassemble Canister and shake loose carbon out of it if any.
 

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Well code came back today so disassemble Evap Canister from it's location and found the pressure sensor almost pulled out from it's position. As far as I can see it's only press fit, so I removed it and greased the "O" rings and put everything back together. Also vacuumed the foam filter inside the canister it was pretty black. Sorry, I failed to take pictures, too concentrated on the fix. Next time I will for sure. One bolt holds the canister in place, of course it broke.


Let the waiting game begin again.
 

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Still waiting!!!
 

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I know all the P0400 series codes are from Driveability issues (emissions control). 420 and 430 are catalytic converter, 440s-460s is an EVAP issue. Check for electronic pressure solenoid, purge valve, and charcoal canister. Its gotta be one of those. I think im a bit late on that though :)
 

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Okay, code came back today and this time decide to take a different approach since I had the car to myself the whole day. So I troubleshooted the problem instead of just changing and guessing. With my Torque APP in hand I started the car and started looking at the readings it gave me, concentrating mostly on Evap info well that's when I came upon the Evap pressure reading (4265) which to me seemed a little high since the guage only goes up to 1100. So I turned the engine "off" and sure enough the readout stayed the same. Should drop down to zero. I went out back and took the one off of the 2010 Cobalt and it read .075. With such a discrepancy this has to be my problem. Reset the code but this time I'm sure it won't come back. Here's a picture of the one I removed.
 

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