My 2008 H3 had the engine light pop on and I connected up my ODB-II device to it, it reads P0446

P0446 - Evaporative Emission Control System Vent Control Circuit Malfunction

Now I brought this to one mechanic who charged me $100 for diagnostics and said "oh it's your gas cap". So I get an OEM Gas cap from Amazon and replaced it.
2 days later the CEL comes on again - same code. SO I call up the mechanic he said "bring it to a dealer". I said "Can I get $100 back for mis diagnosing the issue?" - "NOPE go to a a dealer"
So I bring it to another mechanic. THis guy said he checked it with the smoke machine and found no leaks, tested the circuits (or relays) and found nothing wrong. Well this was was cool because he goes "I cant charge you for something I didnt fix"


Now I can reset the CEL myself every few days but I'd rather have a permanent fix.



Any ideas? Could the ECM be going bad?


*I am expect a dealership to charge me $1000 to fix this (lol)

 

If your 3 drives fine other than that CEL, I would put a bad PCM way, way down the list of possibilities.

The P0442, 445 & 499 all point to a malfunction in the EVAP solenoid vent, simple stuff. I did the fix, my old code was P0442, my favorite code no less. https://www.hummerforums.com/forum/h...control-30289/

Your code aims also at the EVAP purge valve, but still may be related to the above. Check the electrical connectors to each, if it the purge valve is all caked in crud, then tak it apart and blow out any dirty crud. Search some info on the purge valve.

 

Here is some stuff we dug up on gf's h3. ...


https://sites.google.com/site/happyh...0449-resources