Patent ID: 8087291

Claim:
A method for performing a diagnostic on at least one exhaust gas analyzer probe situated in an exhaust system of an internal combustion engine, the method comprising: determining that the engine is operating in a special operating state which includes one of an overrun phase and a quasi steady-state phase; responsive to the determining that the engine is in the special operating state, applying at least one test injection, at least one of a duration and a starting time of the at least one test injection being selected so that no appreciable increase in torque occurs as a result of the at least one test injection; after applying the at least one test injection, obtaining an actual signal characteristic of a signal generated by the probe in response to the at least one test infection; comparing the actual signal characteristic to an expected signal characteristic; and outputting an indication that the probe is faulty in response to determining that a deviation between the actual and the expected signal characteristics exceeds a predetermined threshold.