Methods and systems are provided for diagnosing degradation and/or alteration in an evaporative emission control system of a vehicle. In one example, a method for a vehicle may comprise, during a refueling event, detecting presence or absence of a fuel vapor canister coupled to a vent line of the evaporative emission control system of the vehicle based on a response of a hydrocarbon sensor coupled to the vent line. In this way, hydrocarbon emissions may be reduced by identifying vehicles with tampered or degraded evaporative emission control system.