Self-diagnosis apparatus and method for fuel evaporative emission

摘要

A self-diagnosis apparatus and method for use in a fuel evaporative emission control system for a vehicle having an internal combustion engine. A space part of a fuel tank is coupled with an intake air passage via a vapor passage. Fuel vapors from the fuel tank pass through the vapor passage. A canister is provided in the vapor passage to absorb the fuel vapors from the fuel tank. The internal pressure of the space part of the fuel tank is detected by a pressure detecting unit. The quantity of change in the internal pressure during the lapse of a certain time period is calculated by a calculating unit. The internal pressure change quantity is compared with a predetermined reference value, and thus abnormality is judged by a judgement unit in accordance with the comparison result.