2007 F150 Check Engine Light
 

My check engine light has been on and is giving me the P0446 code. I have cleared the code multiple times and it comes back on. I replaced the gas cap, the canister purge valve and the top hose that comes out of the valve. Still comes on when I restart. I believe the purge valve is not opening and closing. I took the truck to a mechanic I have used for years and he had it for two days. He said it is probably a ground circuit or computer issue. His best suggestion was to not worry about it and cover the light with black tape. Guess I won't be using him any longer. Anyhow, has anyone had the same issue and if it is a computer issue, is that a costly fix that must be dealt with at the dealer?

When we see a code and search it out ,unfortunately not all problems are "bad" sensors or valves.
This code when examined carefully directs us to a possible electrical problem which could come from the PCM, it's connections , the wiring connections maybe something internally wrong with the vent valve itself. This is what separates the men from the boys. Not everyone is electrically up to snuff and they miight hit the cause and might not.
That is why some shops charge what they charge because they went on to learn about how the different systems function. Without that knowledge and information, they are lost.
I'm sure this is not the first time a shop took the easy way out.
Anyway, your best bet is either a good shop with access to the info or hopefully a good dealership service dept.
No matter what I may tell you , there is no guaranty that is the cause because certain tests need to be performed to verify what we suspect.
If it was only that easy.

P0466 is for the vent valve.
You could replace the vent valve and hope that fixes it or pay a good shop/dealer to diag it.
A lot of smaller shops don't touch evap systems because it can be hard to diag a small evap leak.

For some unknown reason, the check engine light went off today. Not sure why. I drove the truck a few times and it didn't come back on. Now I am even more confused!

This could be one of those times when being confused won't cost you any $$$.

So far so good, makes me wonder why it suddenly went off.

Valves are known to stick sometimes, maybe that is all it was, don't know.