Thank you for the info. Is the picture I sent the purge valve?

 

no it is not

 

Thank you for the info. I am attaching a couple of pics. I would like to know if pic 1, is the purge valve?

 

This is pic 2. Is the puge valve and is the hose (with white ring) in this pic the one I remove and then detach the other end at the charcoal canister and the blow air thorough to check for blockage? If yes is there a special way to remove it? I have had the car scanned. What things should a scanner be able to detect?

 

Scanners are not "Replace this Part" devices. They only accompany the diagnostic tables in the factory manual. If a scanner does give you a fault code, then you go straight to the diagnostic chart and follow that.

That is the purge valve in the photo. The attached hose is not going to be completely blocked, causing a P0446. It might have some carbon up in it, but you are working with the wrong hose for a P0446 - your main restriction is in the venting path. If you do blow that hose out, do it from the engine side.

You have to understand how the system works when setting a P0446. See attached document. Each time you meet the conditions in the attachment (cold start), as a pre-programmed test the purge valve opens. The system draws a vacuum on the fuel tank and then closes the purge valve, opening the vent valve. If it still (incorrectly) sees vacuum of after some period of time, then it sets a P0446.

So possibilities for a P0446 are:
1. Faulty vent valve or electrical problem
2. Hose from vent valve to canister blocked
3. Canister blocked
4. Vent port out of vent valve blocked
5. Faulty fuel tank pressure sensor

Problems typically come from people who have to get that last cup of gas in their tank when filling. Typically overloading the carbon canister with gasoline until it eventually fails and pukes carbon into the hoses.

If you want to shotgun some likely parts (should be around $100 from Amazon) - do the canister and the vent valve (super cheap) and blow out the hoses (not the one to the fuel tank pressure sensor). What I did after I first got my Blazer. You can go from there if that doesn't fix the problem.

Also had the same on my 2004 Avalanche right after I bought it. Had to dribble in 30 gallons of gas at each fill. I never "top off" my tank. I just hang it up when it clicks off on full flow. Both have now been just fine for a long time. Blazer = 10 years Avalanche = 6 years

 

Thank you for all of the info. Please clarify which pic I sent to you was of the purge valve. Was it pic one or pic 2?

 

Purge valve is the one with the blue connector pushed into the top.

Remember that the purge valve is not the vent valve.

 

Okay. So I shouldn't do anything with the purge valve? Should blow air through the hose between the vent valve and the charcoal canister...blowing from the engine connection to the back? Is the vent valve in pic 1 or 2 that sent before or neither?

 

Vent valve is back by the charcoal canister near the fuel tank. Purge valve is on the engine and has a blue connector plugged into the top.

If you had a scanner that could read the fuel tank pressure sensor, you could first make sure that sensor is working - but I'm quite sure that you don't have one, or a scanner that will do the diagnostic table as written.

So referring to post #2....... Disconnect hoses #7 and #9 from their respective valves and the charcoal canister. Blow them out. For purge valve hose blow from engine side of hose. Replace the vent valve and the charcoal canister. If still not fixed, then may be something wrong with the the fuel pressure sensor or electronics.

If you can't do the job with these instructions, then I recommend that you take it to someone for repairs.

 

Disconnected line up by engine and back on the charcoal canister..blew it out with air. Also disconnected lower line on charcoal canister and blew air though that line and the canister. All lines clear it seems. Reattached lines. Cleared code. Now have 2 incl monitors that will not complete. I have driven the GM drive cycle ( idle 4 mins..go 55 for 3 mins...coast no brakes etc. at least 5 times....3 last night alone. Have also done the idle 4 mins or more..heat on high...defrost on...drive 30-40 mph...decelerate then repeat and done that for a few days. No change. 2 inc....no c e light...no codes. Still won't pass NY State inspection. Suggestions plz.