Power tailgate control unit has the self-diagnosis function that can detect failure without HDS. If the power tailgate system has a failure, the system will initiate fail-safe mode, and ignition switch turned ON (II), the power tailgate indicator will start to blink. In case the ignition switch is turned ON (II) again, if the tailgate system detects the same reoccurring failure, the system will initiate fail-safe mode and the power tailgate indicator will come on (no blinking).