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So my truck is giving the code P0446 which is evap emission control system vent circuit malfunction. I have read a bunch of the posts on here. They all seem to refer to code 0455. But I am just wondering if changing out my canister will fix this problem. No one seems to say if it fixed their problem when they had code 446. Also if this will fix my problem how much hose will I need to do the cheaper fix, and if someone could give me the part number that would be awesome. From the older posts it seems to have changed over time. Thank you guys for reading and letting me know. If it won't fix it is there something else I should look at?
 

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The truck performs an Emission test to determine if there is a block in the venting. It causes a vacuum to be pulled in the system and then checks to insure that the vacuum is released when commanded. If it holds vacuum, P0446 sets. Barring any wiring problems, it is probably a defective canister vent valve or fuel tank pressure sensor.

You can get a canister vent solenoid valve, part number 214-2149, that should work with a new piece of 5/8" hose. I would suggest to get a couple of feet of hose and trim it on installation and route it to prevent kinks. The valve is available from Amazon for less than $15.

The vent valve that was originally recommended as a cheaper alternative for these trucks, (214-2147), has been changed and now has a square connector receptacle. If you get one, it will require an adapter harness to connect properly.

If the vent valve doesn't fix the problem, the cause could be the Fuel Tank Pressure Sensor. The part number is 16238399 and is also available from Amazon. $24. You have a Regular Cab, so that Sensor can be replaced by removing the left rear wheel well liner and jacking up on the body a bit.

Let us know what happens. Open-ended Threads make the "Search" function more difficult to use, as you have noticed..

You can research the parts for cheaper options. I mentioned Amazon, but they are available elsewhere.
 

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Discussion Starter #4
Thanks for the information cart. I will definitely post on which one fixes the problem I will probably start with the canister and try the other valve later. Hopefully I can get to it tomorrow if not then probably next weekend.
 

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Sorry it took so long to get to it, but I finally got my evap canister switch put in and cleared my code. I will let you know if my CEL comes back on.
 

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If by any chance it doesn't, check the lines first for blockage. I've seen it sometimes. Normally looks like that green varnish you see in small engine carbs from the ethanol reacting with the gas over time when I clear it out.
 

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Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.
 

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Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.

Mine also came back on after changing that thing out. What did you do to fix?
 

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Well it didn't clear my code it came back on while I was driving home. I am going to have my code read again and see if it has changed. I am not sure if I need to clean out the line, I put in a new one with the new switch, but if you think I still should I don't think it will be too difficult to pull it off and blow it out.

Mine also came back on after changing that thing out. What did you do to fix?
I’m in the same boat- I have an 06 2.8l canyon and code po446..replaced gas cap (code)...and vent solenoid (code again)...leaning towards paying a garage now bc I can’t diagnose any further and I’ve exhausted all the internet help I can find...
 

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For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.
 

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For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.


It was the fuel pressure sensor. Replaced by dropping driveshaft.


Sent from my iPhone using Tapatalk
 

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For the P0446 test the ECM opens the purge valve and the vent valve and checks to insure that a vacuum doesn't go above a specific level. The fuel tank pressure sensor tells the ECM what the vacuum is. A high vacuum indicates a blockage somewhere in the system. A leaking fuel cap will not set a P0446 code.

If the vent valve has been positively ruled out, there could be a blockage in one of the tubes or in the canister. Constant "topping off' when refueling can allow raw fuel to penetrate the canister and deteriorate the carbon causing it to break apart.. If the fuel tank pressure sensor is defective it could be sending erroneous info to the ECM.

The fuel tank pressure sensor is mounted on the top of the pump module. It can be accessed, without dropping the tank, on a Std Cab or Ext Cab. I think the tank has to be dropped on a Crew Cab.
I have not found a diagram of the emission lines. At the canister, There is the one which goes from the canister to the Vent valve sol, then 2 others.
I assume the large diameter line (1/2 or 5/8?) goes to the gas tank and the smaller (about 1/4") goes to the purge valve on the side of the Engine? I blew into both w/compr air. The small one seemed like I was blowing against a closed line which I think is correct since the Purge valve should be closed. I removed the gas fill cap, installed a funnel to keep the flap open then blew into the larger line, it sounded like the tank was inflating. Now I've read that there is a check valve? Is that in the plastic line or the fuel pump module fittings? Does the line have to be blow out from the tank end to make sure there are no restrictions?
This is 9-17-18; I started addressing this P0446 code in March 2018. Each time I erase the code & make a change, the code doesn’t come back for a long time, so it’s getting drawn out. 1st, the Vent solenoid had over a 100 ohms resistance, so I replaced it and the tube that came with it, eventually P0446 came back. Then I verified that the new vent vlv still only had 21.4 ohms then tested the purge valve. The Purge held vacuum on both the inlet & outlet and had 22.2 ohms and 12v go to it w/the key on. P0446 came back so I installed an AC Delco gas cap, the code came back. So now I’m wondering about a restricted line, before I replace the Fuel Tank Pressure sensor. I’ve read that on my Reg cab, the sensor can be changed w/o dropping the tank or removing the bed, just by removing the inner wheel opening liner? Is this correct? Thanks for your helpful posts. I have 05 Reg Cab I5

What does 700 Nation stand for?
 

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Reg. Cab , have to loosen Bed bolts passenger side, take out bed bolts driver side.
Remove Driver side rear plastic inner fender.
Disconnect filler and vent tube.
Lift and block Bed on driver side.
Clean top of tank, water-soap-water- dry and wipe
 

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Reg. Cab , have to loosen Bed bolts passenger side, take out bed bolts driver side.
Remove Driver side rear plastic inner fender.
Disconnect filler and vent tube.
Lift and block Bed on driver side.
Clean top of tank, water-soap-water- dry and wipe
Thank you very much, I appreciate the info.
 
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