Gas sensor diagnosis device

A gas sensor diagnosis device for a gas sensor of a mixed potential type, the gas sensor comprising a sensor element arranged to be exposed to a detection target gas, the sensor element generating and transmitting a mixed potential to the gas sensor diagnosis device when the sensor element is heated at an activation temperature within a predetermined activation temperature range,

• the gas sensor diagnosis device comprising a central processing unit being configured to provide:
• a temperature change part which varies a temperature of the sensor element to a first temperature which is outside of the predetermined activation temperature range;
• a zero-voltage shift detection part which detects whether the mixed potential of the sensor element is not more than a predetermined output threshold value of the sensor element after the temperature change part varies the temperature of the sensor element;
• a temperature acquisition part which detects a zero-voltage shift temperature of the sensor element at which the zero-voltage shift detection part detects that the mixed potential of the sensor element is shifted to not more than the predetermined output threshold value;
• and
• a deterioration state detection part which detects whether the sensor element has been deteriorated on the basis of the zero-voltage shift temperature of the sensor element detected by the temperature acquisition part.