An abnormality judging section detects the occurrence of an abnormality based
on various signals input to a master control CPU, and judges that abnormal event.
A data selecting section selects inherent data which is inherent to the abnormal
event in accordance with the judged abnormal event from data input to the master
control CPU and data generated in the master control CPU. A writing section writes
the freeze-frame data to an EEPROM together with nine common data irrespective
of a difference in abnormal events. A reading section reads desired freeze-frame
data from data stored in the EEPROM in accordance with a request from a diag tester.
