| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a device for diagnosing a failure in a NO<SB>X</SB>sensor. <P>SOLUTION: This NO<SB>X</SB>sensor 1 causes an oxygen pump cell to eliminate oxygen from an exhaust gas coming into the sensor thereby lowering the concentration of oxygen in the exhaust gas to a prescribed concentration while monitoring the oxygen concentration by means of an oxygen concentration monitoring cell. Thereafter, NO<SB>X</SB>in the exhaust gas is decomposed by an oxygen generating cell to newly generate oxygen. Thereafter, the concentration of oxygen in the exhaust gas is detected by an oxygen concentration detecting cell, thereby detecting the concentration of NO<SB>X</SB>in the exhaust gas. The monitoring cell outputs an output value corresponding to the concentration of oxygen in the exhaust gas. A specific voltage is impressed on the pump cell when the concentration of oxygen in exhaust gas coming into the sensor is known. If the output value outputted from the monitoring cell is shifted from a value at which the output value is supposed to be able to stand when the monitoring cell is normal, the sensor is diagnosed as being out of order. <P>COPYRIGHT: (C)2007,JPO&INPIT |
