Abnormality Diagnostic Device and Abnormality Diagnostic Method for Booster

An abnormality diagnostic method for a booster including:

• a negative pressure pump that generates a negative pressure;
• a negative pressure chamber into which the negative pressure generated by the negative pressure pump and an intake pipe negative pressure of an internal combustion engine are introduced;
• and a pressure sensor that measures a pressure in the negative pressure chamber, the booster boosting a brake operating force by a negative pressure in the negative pressure chamber,
• the abnormality diagnostic method comprising:
• a first step of determine a change in a measured pressure value obtained by the pressure sensor, in a state in which the negative pressure pump is stopped and in a condition in which the pressure in the negative pressure chamber decreases due to the intake pipe negative pressure of the internal combustion engine;
• a second step of determining a change in a measured pressure value obtained by the pressure sensor, in a state in which the negative pressure pump is operated and in a condition in which the pressure in the negative pressure chamber decreases due to the negative pressure generated by the negative pressure pump;
• and
• a third step of receiving the change in the measured pressure value determined in the first step and the change in the measure pressure value determined in the second step, to generate abnormality diagnostic information for each of the negative pressure pump and the pressure sensor.