| 摘要 |
PURPOSE:To securely decide the fault of the air fuel ratio sensor by outputting a fault signal unless the electromotive force of the sensor cell of the air fuel ratio sensor enters a set area where the fault is decided. CONSTITUTION:A fault decision means fetches the electromotive force Vs fo the sensor cell 20 from a detecting circuit 38 and functions to decide sensor cell fail unless the input value is within specific permissible width phi-phi. A 2nd fault decision means fetches air fuel ratio signals (Vout, Vstc) from 1st and 2nd air fuel ratio detecting means and decides pump cell fail unless the input values are within specific permissible width of normal values, thereby outputting a pseudo signal. An in-fault stop processing means cooperates with a pump cut circuit 39 to output a pseudo signal showing that a detection chamber 25 is held in a stoichiometry state. |
