Method for monitoring the performance reliability of a control unit and diagnostic device

A method for monitoring, via a diagnostic device, a performance reliability of at least one of a control unit and at least one sensor of a safety device for protecting a vehicle occupant, the diagnostic device being arranged in a motor vehicle together with the control unit and the at least one sensor and the diagnostic device including an arrangement for coupling to the at least one sensor of the safety device, comprising the steps:

• a) recording, via the coupling, an impact;
• b) deriving a value for an impact severity from the impact;
• c) comparing, by a comparator of the diagnostic device that provides a predefined threshold value for a proper functioning of the at least one of the control unit and the at least one sensor, the value for the impact severity to the predefined threshold value;
• and
• d) outputting, by an output device of the diagnostic device, an error-function signal in the event that the value for the impact severity exceeds the predefined threshold value, the error-function signal indicating that a proper functioning is no longer ensured for the at least one of the control unit and the at least one sensor;
• wherein the predefined threshold value is lower than a threshold value provided for a triggering of a restraining arrangement assigned to the at least one of the control unit and the at least one sensor.