Image Number 13 for United States Patent #4870942.
A diagnosis device for an exhaust gas recycling device diagnoses whether or not an exhaust gas recycling device is operating normally; the temperature of an exhaust gas recycling passage is detected by a temperature detection means, a decision is made by an exhaust gas recycling operating region detection means whether or not the operating region is such as to carry out exhaust gas recycling, when a decision is made that the operating region is such as to carry out exhaust gas recycling a counter is incremented and when otherwise is decremented, and a decision that the exhaust gas recycling is not being carried out normally, that is that the exhaust gas recycling device has failed, is made when the count value of this counter is at least a certain value and the temperature of the exhaust gas recycling passage is not more than a certain value.
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