Method for diagnosing exhaust gas sensors

A method for diagnosing electrical lines of a wideband lambda sensor, each respective electrical line of the electrical lines of the wideband lambda sensor being connected to a respective terminal of an evaluation and control unit, the evaluation and control unit being configured to operate the wideband lambda sensor, each respective terminal of the electrical terminals having assigned to it a respective electrical switch via which each of the terminals is capable of being individually connected to at least one defined electrical potential, wherein each of the switches is voltage-resistant against a maximum short-circuit voltage that is to be expected at the respective terminal in case of fault, the method comprising:

• respectively closing exactly one of the electrical switches at a time, one after the other, and ascertaining a current assigned to the respective electrical terminal, or a variable representing the current;
• and
• (i) subsequently, in a case in which it is already known that there is a short circuit in one of the electrical lines, the short circuit being assigned to a line of the electrical lines that is connected to a terminal of the respective terminals at which the current having a highest magnitude was ascertained, and/or (ii) comparing a magnitude of a largest current of the ascertained currents to a specified or temperature-dependent threshold value and, when the magnitude exceeds the threshold value, inferring that there is a short circuit, and the short circuit is assigned to a line of the electrical lines that is connected to a terminal of the respective terminals at which the current having the largest magnitude was ascertained.

A method for diagnosing electrical lines of a wideband lambda sensor, each respective electrical line of the electrical lines of the wideband lambda sensor being connected to a respective terminal of an evaluation and control unit, the evaluation and control unit being configured to operate the wideband lambda sensor, each respective terminal of the electrical terminals having assigned to it a respective electrical switch via which each of the terminals is capable of being individually connected to at least one defined electrical potential, wherein each of the switches is voltage-resistant against a maximum short-circuit voltage that is to be expected at the respective terminal in case of fault, wherein the defined electrical potential can assume two different defined values, the method comprising:

• respectively closing exactly one of the electrical switches at a time, one after the other, and ascertaining a current assigned to the respective electrical terminal, or a variable representing the current;
• and
• (i) subsequently, in a case in which it is already known that there is a short circuit in one of the electrical lines, the short circuit being assigned to a line of the electrical lines that is connected to a terminal of the respective terminals at which the current having a highest magnitude was ascertained, and/or (ii) comparing a magnitude of a largest current of the ascertained currents to a specified or temperature-dependent threshold value and, when the magnitude exceeds the threshold value, inferring that there is a short circuit, and the short circuit is assigned to a line of the electrical lines that is connected to a terminal of the respective terminals at which the current having the largest magnitude was ascertained;
• wherein for each respective line of the electrical lines, a first current is measured while the defined potential has a first value, and a second current is measured while the defined potential has a second value different from the first value.