CEL code PO446 won't reset
 

Thanks to this forum, I was able to clear EVAP leak codes (PO442, PO445) by removing and testing Charcoal Canister Shut Off Valve. I then received a PO446 (EVAP Emission ControlSystem vent Circuit Malf). I tested voltage to Shut Off Valve, only was getting 6v, (ground was bad). I connected ground wire to a body ground, voltage now OK, but PO446 keeps on coming back. Would I need to trace ground back to origin (please help w/ location - 2000 W210) or is it likely that I need to replace valve.

Thanks,

Alan