check engine light on

[captain6liter]

My question is what is the most common problem associated with this fault ? And where are the componets located?

[GM-Tech]

Year? Model? Engine?

 

Most common is a gas cap left loose... I'm sure I don't have to tell you where that's at. Next would be the bad vent valve... on top of the gas tank in most pickups. You can probably see it by looking through the gap between the bed and the cab on the driver's side.

[captain6liter]

Year? Model? Engine?

 

Most common is a gas cap left loose... I'm sure I don't have to tell you where that's at.  Next would be the bad vent valve... on top of the gas tank in most pickups.  You can probably see it by looking through the gap between the bed and the cab on the driver's side.

 

<{POST_SNAPBACK}>

 

 

The year is 2004 GMC,2500hd,6.0 liter,Yes the cap is tight.Cannot see any valve between cab and box.I,m thinking its attached to the rear of the fuel tank near the top ???

[GM-Tech]

Extended cab, crew cab?

[captain6liter]

Extended cab, crew cab?

 

<{POST_SNAPBACK}>

 

 

Extended cab

[GM-Tech]

Looks like it's attached near the front of the evap canister which is on the front of the tank.

[GM-Tech]

OOOPS. For some reason, I read your first post as the truck having a P0442 and I see now that it's really a P0446.

 

Still could be a vent valve problem, which is involved in this test, but it could also be the purge solenoid (top front of intake) or a blocked. This needs some extensive diagnosting testing with a Tech 2 scanner, but if I had to guess, I'd stlll say vet valve.

[Norseman]

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