Abstract: A diagnosis method and a gas sensor that is adapted to perform the diagnosis method are described for detecting a damage of a gas sensor causing a malfunction, particularly a crack, wherein the gas sensor has at least two chambers with one chamber comprising a reference gas. The method includes pumping out gas of one of the chambers, measuring a value of a variable being proportional to the concentration of the gas as a function of time, comparing the measured variable value and/or the measured time to a predetermined threshold, detecting a damage of the sensor if the measured variable value and/or the measured time is outside the interval of normal mode of operation defined by the corresponding predetermined threshold.

Abstract: A diagnostic method for testing malfunction of a Selective Catalytic Reduction (SCR) exhausts aftertreatment system of an internal combustion engine. The method measures and registers a first mean NOx sensor value for a normal mass flow level of a fluid reducing agent, then a second mean NOx sensor value related to a higher mass flow level is measured and registered. The two registered NOx sensor values are compared and it is determined if, on one hand, the first value is higher than the second value, or, on the other hand, the first value is lower than the second value. The cause of the malfunction may be found in the dosing system or in the SCR catalyst.

Abstract: A diagnosis method and a gas sensor that is adapted to perform the diagnosis method are described for detecting a damage of a gas sensor causing a malfunction, particularly a crack, wherein the gas sensor has at least two chambers with one chamber comprising a reference gas. The method includes pumping out gas of one of the chambers, measuring a value of a variable being proportional to the concentration of the gas as a function of time, comparing the measured variable value and/or the measured time to a predetermined threshold, detecting a damage of the sensor if the measured variable value and/or the measured time is outside the interval of normal mode of operation defined by the corresponding predetermined threshold.

Abstract: A diagnostic method for testing malfunction of a Selective Catalytic Reduction (SCR) exhausts aftertreatment system of an internal combustion engine. The method measures and registers a first mean NOx sensor value for a normal mass flow level of a fluid reducing agent, then a second mean NOx sensor value related to a higher mass flow level is measured and registered. The two registered NOx sensor values are compared and it is determined if, on one hand, the first value is higher than the second value, or, on the other hand, the first value is lower than the second value. The cause of the malfunction may be found in the dosing system or in the SCR catalyst.