Patent ID: 8512531

Claim:
A gas concentration detection apparatus comprising: a gas sensor that includes a gas concentration detection cell and an oxygen pump cell, wherein the oxygen pump cell changes a concentration of oxygen in a measurement target gas and removes excess oxygen from the measurement target gas, and the gas concentration detection cell detects a concentration of a specific gas component in the gas whose oxygen concentration is changed by the oxygen pump cell; and an electronic control unit having control logic configured to cause the electronic control unit to: form a deterioration judgment about the gas sensor in accordance with a cell output from the gas concentration detection cell; and form a deterioration judgment about the gas sensor during a warm-up of the gas sensor and execution of the oxygen pump cell in accordance with the cell output obtained before an inflection point appears in the cell output of the gas concentration detection cell, wherein the inflection point is a point at which oxygen in an internal space of the gas sensor is substantially removed by the oxygen pump cell.