| 摘要 |
Method and apparatus for field testing and diagnosing at least one NO x -sensor in a diesel engine exhaust system. The field testing apparatus being connectable to a truck having a lean burn diesel type engine, via an onboard diagnostic connector. The field testing apparatus is arranged to initiate a test cycle, and to diagnose at least one NO x -sensor in an exhaust system of the truck. The test cycle is performed on a running engine as a test sequence in a stationary truck, in at least two different states of operation, while NO x related values issued by the at least one NO x -sensor are measured over a predefined period of time. At least one state of operation is obtained by simultaneously opening the exhaust gas recirculation valve and controlling the back pressure valve for increasing backpressure. A dedicated algorithm is used to compare the measured values to a predefined model, and to provide a numerical summary and statistical evaluation of the sensor functioning. The numerical summary being indicative of a likelihood of the at least one NO x -sensor behaving correctly, and thereby enables a well founded decision as to whether or not the at least one NO x -sensor requires replacement. |
