Abstract: A method for diagnosing a purge line path of a tank ventilation system of a motor vehicle operated by an internal combustion engine is provided. The purge line path extends between a fuel vapor retention filter and an intake manifold of the motor vehicle, and includes a tank ventilation valve, a pressure sensor, a purge line path region arranged upstream of the pressure sensor, a purge line path region arranged downstream of the pressure sensor, a full load purge path arranged between the tank ventilation valve and the intake manifold, and a part load purge path arranged between the tank ventilation valve and the intake manifold. A plurality of part diagnoses are carried out temporally one after another for diagnosing the purge line path in the case of an active tank ventilation function, and pressure signals measured by the pressure sensor are evaluated within the context of the part diagnoses.