Abstract: In a thermostat failure diagnosis apparatus for an internal combustion engine in which a failure diagnosis of a thermostat can be effectively made, in the case where, after starting of the engine, an intake air quantity of the engine or a parameter related to the intake air quantity is equal to or higher than a predetermined value, and a cooling water temperature is equal to or higher than an intake air temperature (outside air temperature), on the basis of a time in which a rising quantity in the cooling water temperature at an upstream side of the thermostat reaches a predetermined value, or a time in which the cooling water temperature rises to a predetermined temperature, the failure of the thermostat is judged. By this, the failure diagnosis of the thermostat can be rationally made only when the engine generating heat quantity is large to some degree to prevent erroneous diagnosis.

Abstract: In a thermostat failure diagnosis apparatus for an internal combustion engine in which a failure diagnosis of a thermostat can be effectively made, in the case where, after starting of the engine, an intake air quantity of the engine or a parameter related to the intake air quantity is equal to or higher than a predetermined value, and a cooling water temperature is equal to or higher than an intake air temperature (outside air temperature), on the basis of a time in which a rising quantity in the cooling water temperature at an upstream side of the thermostat reaches a predetermined value, or a time in which the cooling water temperature rises to a predetermined temperature, the failure of the thermostat is judged.

Abstract: In a thermostat failure diagnosis apparatus for an internal combustion engine in which a failure diagnosis of a thermostat can be effectively made, in the case where, after starting of the engine, an intake air quantity of the engine or a parameter related to the intake air quantity is equal to or higher than a predetermined value, and a cooling water temperature is equal to or higher than an intake air temperature (outside air temperature), on the basis of a time in which a rising quantity in the cooling water temperature at an upstream side of the thermostat reaches a predetermined value, or a time in which the cooling water temperature rises to a predetermined temperature, the failure of the thermostat is judged.

Abstract: A fault diagnosing apparatus for evapopurge systems, including a device adapted to detect a pressure in the interior of an evapopassage including a fuel tank, a depressurization device adapted to close a first valve provided in an atmosphere-opened port of a canister and depressurize the interior of the evapopassage by a negative pressure occurring in a suction passage of an internal combustion engine, a repressurization device adapted to close a second valve after the operation of the depressurization device finishes, to repressurize the interior of the evapopassage, and a fault judgement device adapted to allow a judgement, which is based on an output from the pressure detecting device, that an evapopurge system is abnormal to be given on condition that the depressurization and repressurization devices are operated plural times.