SENSOR-MALFUNCTION DIAGNOSIS DEVICE

摘要

The purpose of the present invention is to inhibit the occurrence of erroneous diagnosis in sensor-malfunction diagnosis. A sensor, which detects NOx and ammonia in an exhaust gas discharged from a selective reduction NOx catalyst using ammonia as a reductant, and in which the ammonia reacts with the NOx, is provided further towards a downstream side than the NOx catalyst. A sensor-output reduction amount generated as a result of the ammonia reacting with the NOx in the sensor is calculated on the basis of the NOx and ammonia discharged from the NOx catalyst, and sensor-malfunction diagnosis is performed on the basis of the output reduction amount.