Vehicle evaporative system diagnostic

摘要

A diagnostic method for an evaporative emission control system of an automotive vehicle determines functionality of one of a purge valve (16) and/or a vacuum switch and valve assembly (14). The vacuum switch and valve assembly (14) is located between a carbon canister (12) and atmosphere and is either open or closed according to whether the system is in a high or low negative pressure condition. A controller (18) determines if the vacuum switch and valve assembly (14) is functioning properly according to the high or low negative pressure condition. The controller (18) determines if the purge valve is functioning properly based on engine performance characteristics.