METHOD AND DEVICE FOR DIAGNOSIS FOR VEHICLE

Forced activation signal supplier 550 supplies a forced activation signal Sx to a diagnostic target part 101 related to a diagnostic item requiring a forced activation signal. Vehicle-state detector 552 detects a current state of the diagnostic target part 101 through an ECU 1. Diagnostic element 553 compares the currently detected state of the diagnostic target part 101 with a state predicted when the forced activation signal Sx is given to diagnose the diagnostic target part 101. When the forced activation signal Sx is supplied to the part of the vehicle, self-diagnosis stopping element 554 gives an instruction to stop a self diagnosis for at least an item the diagnostic result of which may vary under the influence of the forced activation signal Sx, or to invalidate the diagnostic result.