| 摘要 |
PURPOSE:To detect a failure related to the heater performance of an air-fuel ratio sensor having a heater with high accuracy, while a detection opportunity for the failure being properly maintained. CONSTITUTION:An electronic control unit (ECU) 51 controls power fed to the heaters 38a to 41a of respective air-fuel ratio sensors 38 to 41, depending upon the operation condition of an engine 1 or the temperature condition of exhaust passages 5L, 5R, 15L and 15R, thereby adjusting the temperature of the sensors 38 to 41. The ECU 51 forcibly interrupts power fed to each of heaters 38a to 41a for the predetermined time, whether the heaters 38a to 41a are electrically energized or not, upon judgement that the operation condition of the engine 1 is not adversely influenced due to the interruption of power. Also, the ECU 51 after interrupting the power, compares the value of current flowing to the heaters 38a to 41a with a reference value, while supplying power thereto, and makes judgement about a failure related a drop in the performance of the heaters 38a to 41a on the basis of the comparison result. |
