Charcoal Canister Seal
 

Getting the Gross Leak OBD Code.
found that I am missing the rubber seal/grommet where the Purge Valve goes into the Vapor canister.

Outside of buying a new canister, is there anything I can do/use to remedy this?

Thanks

Possibly go to a junkyard and take a seal of an HHR, cobalt or cruze. Maybe all gm cars have this seal also.
Or PM hellshotrod on this forum.

unfortunately, not having any junkyard luck with this.

Oh, yes. This was my issue. My Vapor Canister Vent Valve failed last summer. Easy 10 minute fix. Bought a new one. Got the gross leak P0455 code. I thought it was because I bought the "Standard" brand name instead of AC Delco. Months later I found a rubber O ring on the garage floor. Never put 2 and 2 together. Threw the O ring away. Then I finally got around to troubleshooting that code. I took out the Vapor Canister Vent Valve and realized I was I was an idiot. Of course you can't buy that seal if your life depended on it.

So here's what I did last fall. A heater hose is about the right size to go around the tube. But it's too thick to fit into the canister opening. So I cut a thin slice of the hose, like an olive slice, and used black electrical tape to secure it. I positioned it so that it pushed up against the Vapor Canister. That got rid of the Gross Leak. Then I got a Small Leak code P0442. I was at least making progress. I left it alone for the winter. When all is said and done these two codes don't really affect the car. They are just annoying.

March came and I had to fix it for emissions testing and plate renewal. I decided to seal the edge with a little bead of silicone. It worked great. No more code. Passed emissions.

Doc brown
Won't the heater hose be affected from gas fumes ?

It's been on there since October. I took it off to try another Vent Valve thinking that a new Delco one might come with that O ring. But it looked jut fine. What I thought might break down was the black tape. It was fine and the glue on the tape was good as new. I don't think there is much vapor going through there. If you follow the tube up from the Vent Valve it's an open end next to your filler tube. You don't see it because of the plastic cover around the filler tube. If there was that much vapor going through they would not leave it open ended.

On my Sierra that tube wraps around the top of the transmission and hangs off the right side with a small foam filter on the end. And I think that's only there to prevent dirt from going in the tube.

That's because the vent "gulps" air. The purge valve sucks vapor. Thus the names "vent" and "purge"

I strongly suggest, replace the part and oring or just buy the oring only. Your favourite parts palace should be able to match up those for you.

I actually solved it with dipstick tube grommet.
It was just about the same size. Had to cut off a tiny bit.
Pit it on and my cel went off by itself!

Great fixed.