I am getting a PO446 (EVAP Emission Control System Vent Circuit Malf) error. Both the Charcoal Canister Shut-off Valve and Purge Valve are only getting ~6.6V through connector with ignition on, but 12V when connected to a chasis ground. Jumping ground doesn't eliminate code. Does anyone know where I might look for the problem (common isolated ground point?), or is this the correct voltage?