Possible causes – Faulty EVAP Vent Solenoid– EVAP Vent Solenoid harness is open or shorted– EVAP Vent Solenoid circuit poor electrical connection When is the obd code mean? The Powertrain Control Module (PCM) has detected the EVAP Vent Solenoid circuit was low Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P1646 GMC…