A computer apparatus includes a first processor, a second processor, and a main memory. The computer apparatus further includes a memory-diagnostic unit, a diagnostic-program loading unit, and a defective-function identifying unit. The memory-diagnostic unit causes the second processor to execute a memory-diagnostic program to diagnose the main memory, and identifies a defective area in the main memory. The diagnostic-program loading unit loads a processor-diagnostic program for diagnosing a plurality of functions of the first processor into an area of the main memory other than the defective area identified by the memory-diagnostic unit. The defective-function identifying unit causes the second processor to execute the processor-diagnostic program loaded by the diagnostic-program loading unit, and identifies a defective function that is disabled from the functions of the first processor.