Patent ID: 7948240

Claim:
An abnormality diagnosing apparatus for a glow plug provided in an internal combustion engine, wherein the glow plug is energized by power supply from a battery during a glow period from the starting of the engine to the completion of the engine starting, wherein the battery is charged to an appropriate charged state via power generation from an alternator, the apparatus comprising: a tentative-determination section for determining a possible abnormality, wherein, on the basis that power output of the alternator is within a predetermined appropriate range, the tentative-determination section determines if a variation in the power output of the alternator is not more than a reference value when the glow plug changes from an energized state to a de-energized state at the end of the glow period, the reference value being a value set for determining presence of an abnormality in the glow plug, and wherein, on the basis that the variation in the power output of the alternator is not more than the reference value, the tentative-determination section determines that there is a possibility of an abnormality in the glow plug; an affirming section for affirming that an abnormality occurred in the glow plug, wherein, when the tentative-determination section determines that there is a possibility of an abnormality in the glow plug, the affirming section operates to energize the glow plug temporarily after the end of the glow period, wherein, on the basis that the power output of the alternator is within the appropriate range, the affirming section determines if the variation in the power output of the alternator is not more than the reference value when the glow plug is energized, and wherein, on the basis that the variation in the power output of the alternator is not more than the reference value, the affirming section determines that an abnormality has occurred in the glow plug; a modifying section, wherein, based on the tentative-determination section determining that there is a possibility of an abnormality in the glow plug, the modifying section modifies an upper limit of the appropriate range by increasing the upper limit.