IMAGE FORMING APPARATUS, DIAGNOSTIC PROGRAM FOR IMAGE FORMING APPARATUS, AND DIAGNOSTIC SYSTEM FOR IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To reduce load on a user in diagnosis of an apparatus that has an unknown problem, by composing a diagnostic function of an image forming apparatus at a low cost without adding components.SOLUTION: In the startup of the device, a reflection type concentration sensor 14 used by a toner quantity adjustment part 23 is actuated. Also an intermediate transfer conveyance belt 16 is rotated. For a period equal to or longer than one rotation of an intermediate transfer conveyance belt 16, a change in the output level of the reflection type concentration sensor 14 is measured. Quantities of characteristics concerning items different from each other in measured waveform are extracted by a characteristic quantity extraction part 26. Based on a diagnostic matrix 31 specifying the condition of the apparatus by a combination of the quantities of the characteristics, the presence or absence of fracture, breakage, or the like is diagnosed as the present condition of the intermediate transfer conveyance belt 16. If quantity of characteristics from which normal or abnormal determination cannot be made is extracted, a user is informed of this fact. Also, based on an instruction given by the user, the unknown diagnostic data and a condition diagnosed by the user are added to the diagnostic matrix 31.