hey gusy go ta P0446 code, evaporative emission control system (EVAP) vent control circuit malfunction

now i have replaced both the purge valve and vent valve on the car....the one under the hood and the one behind the drivers side rear wheel...still got this code...i want to check if there is a signal at the connector at the back to the vent valve but i was told the negative on these cars is turned on by the pcm....how would i go about diagnosing this without a scan tool....