To provide an information on the failure probability or future reliability of a controller by detecting and storing other data in addition to the working time of the controller and sending the information on the controller.

The momentary temperature detected by using the measuring technique of a controller is read (22) and a questioning section (23) which finds whether the momentary temperature is higher or lower than an already stored maximum temperature TMAX follows. When the answer is 'yes', the momentary temperature is stored in a RAM storage cell. 'TMAX' (24). Successively and, when the momentary temperature is not higher than the stored maximum temperature TMAX, a question is put for detecting the position of an ignition switch (answering section 25). When the ignition switch is not disconnected, a temporary temperature is read (22). When the answer is 'yes', the temperature stored in the RAM cell 'TMAX' is transferred to and stored in a nonvolatile memory within the frame of a post-sequence phase 26 (27). Thus the information on the failure probability and future reliability of the controller are outputted.