| 摘要 |
PURPOSE:To enable the detection of disconnection in signal line by a discrimination that a particular condition continues longer than a first preset time period and that an input from the air-fuel ratio sensor into an electronic control means continues to represent a lean condition of fuel longer than a second preset time period. CONSTITUTION:In a signal line 70 interconnecting an air-fuel ratio sensor 29 to the input-output interface 58 of an electronic control means 41 which calculates a fuel injection amount and the like, a high resistance resistor 71 is connected in parallel to the sensor 29, and the terminal 72 of the resistor 71 is connected to the inversion terminals of operation amplifiers 74 and 76 respectively through resistors 73 and 75, and further connected to the interface 58 through the uninversion terminals of the amplifiers 74 and 76. In this instance, another resistor is provided between a terminal 77 of a predetermined positive voltage and an earth so as to make the uninversion terminal of the amplifier 74 have a voltage higher than that of the amplifier 76. By this, when a condition in which an engine temperature and an engine rotation number are higher than the respective predetermined values continues longer than a preset time period, after an increase in fuel injection amount is confirmed, a discrimination of disconnection in the line 70 is made in case of the output from the sensor 29 representing the lean condition of fuel for a longer time than a preset time period. |
