Evap vent valve location
August 24th, 2011, 7:55 PM
#2
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Come one, somebody has to know where the damn canister vent valve is located.
I've been under the vehicle. The canister is in plain sight, right in front of the fuel tank. I see three lines coming off it. One goes up front, the other two disappear over the top of the fuel tank. If the vent valve is up there the tank is going to have to come down to access it. I'd rather not do that until I'm certain that it's necessary.
I've been under the vehicle. The canister is in plain sight, right in front of the fuel tank. I see three lines coming off it. One goes up front, the other two disappear over the top of the fuel tank. If the vent valve is up there the tank is going to have to come down to access it. I'd rather not do that until I'm certain that it's necessary.
September 16th, 2011, 11:41 AM
#6
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Okay, here's a little update.
I just acquired this vehicle and it was throwing a code P0446 which is supposedly an obstruction somewhere in the vent valve chain.
I lowered the gas tank to get at the vent valve. It isn't necessary to completely drop it to do that. Remove the front two straps (15mm) and undo the charcoal canister from the floor of the car (one nut 10mm). Then loosen the rearmost strap a little and the front of the tank will lower nicely. Be careful not to stress the fuel lines going to the filter.
The vent valve slides off it's bracket in the direction of the driver's side of the car. There's a little tab that has to be released to allow this. I used a small screwdriver to get underneath the tab and open it.
The original vent valve was indeed faulty but it wasn't plugged and neither was anything else. I managed to free it up and reinstall it but the code reoccurred. I then dropped the gas tank completely and still couldn't find anything obviously wrong. I did an electrical check to the extent of verifying that there was 12VDC where it should be. At this time I installed a new vent valve and also a new fuel tank pressure sensor.
After putting it all back together and doing a few runs, the EVAP readiness monitor successfully completed with no code.
The fuel tank pressure sensor just pushes into a hole in the fuel pump module assembly. (now that's one pricey little item) Care is required when removing the sensor. I broke off the tip that goes down inside the module. Fortunately there was just enough sticking up to grab with a pair of cutting pliers and wriggle out. A little silicone spray eased the way for the new one to go in.
This is not a difficult or particularly time-consuming repair, however it does require either access to a lift or a good floor jack and a set of LARGE jackstands. A cordless impact driver for the strap bolts is a big help also.
EDIT: I should add that this is specific to the front wheel drive model.
I just acquired this vehicle and it was throwing a code P0446 which is supposedly an obstruction somewhere in the vent valve chain.
I lowered the gas tank to get at the vent valve. It isn't necessary to completely drop it to do that. Remove the front two straps (15mm) and undo the charcoal canister from the floor of the car (one nut 10mm). Then loosen the rearmost strap a little and the front of the tank will lower nicely. Be careful not to stress the fuel lines going to the filter.
The vent valve slides off it's bracket in the direction of the driver's side of the car. There's a little tab that has to be released to allow this. I used a small screwdriver to get underneath the tab and open it.
The original vent valve was indeed faulty but it wasn't plugged and neither was anything else. I managed to free it up and reinstall it but the code reoccurred. I then dropped the gas tank completely and still couldn't find anything obviously wrong. I did an electrical check to the extent of verifying that there was 12VDC where it should be. At this time I installed a new vent valve and also a new fuel tank pressure sensor.
After putting it all back together and doing a few runs, the EVAP readiness monitor successfully completed with no code.
The fuel tank pressure sensor just pushes into a hole in the fuel pump module assembly. (now that's one pricey little item) Care is required when removing the sensor. I broke off the tip that goes down inside the module. Fortunately there was just enough sticking up to grab with a pair of cutting pliers and wriggle out. A little silicone spray eased the way for the new one to go in.
This is not a difficult or particularly time-consuming repair, however it does require either access to a lift or a good floor jack and a set of LARGE jackstands. A cordless impact driver for the strap bolts is a big help also.
EDIT: I should add that this is specific to the front wheel drive model.
Last edited by The Doctor; September 18th, 2011 at 11:56 AM.
September 17th, 2011, 7:41 PM
#7
Thanks for the update.
I wouldn't have suspected the FTP sensor unless there were specific codes like P0452 or P0453 or multiple EVAP codes that depend on accurate FTP sensor readings.
I wouldn't have suspected the FTP sensor unless there were specific codes like P0452 or P0453 or multiple EVAP codes that depend on accurate FTP sensor readings.
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September 18th, 2011, 12:01 PM
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I ran across a post on another forum where an owner claimed to have replaced everything else before he hit on the FTP sensor. Lacking a scan tool, I figured it was worth a shot.
September 20th, 2011, 4:03 PM
#9
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I have a 2005 Tahoe and I keep pulling the same code. I was wondering where the valve is located on this particular vehicle. I believe it is on the passenger side near the frame rail by the rear set of doors. If anyone has any ideas that would be great.
September 21st, 2011, 7:21 AM
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Shane, try googling "Tahoe p0446". Apparently this is a very common problem with Chevy trucks and there may be an improved valve available from GM for your vehicle.