Device and method for diagnosing an exhaust gas sensor

A device for diagnosing an exhaust-gas sensor for an internal combustion engine, comprising:

• a first terminal connected to a first electrode of a first cell of the exhaust-gas sensor;
• a second terminal connected to a second electrode of a second cell of the exhaust-gas sensor;
• a third terminal connected to a node between a second electrode of the first cell and a first electrode of the second cell of the exhaust-gas sensor;
• a first current source coupled to said first terminal for generating a first current and applying the first current to the first cell;
• a second current source coupled to said second terminal for generating a second current and applying the second current to the second cell;
• and
• a diagnostic device connected to said first and second current sources and configured to:
• control said first and second current sources in a coordinated fashion in order to generate the first and second currents as coordinated currents with respectively predefined signs;
• and
• determine one or more of the first, second, and third voltages when the respective first and second currents are present at said first terminal, and/or said second terminal, and/or said third terminal, and to relate absolute values thereof to the coordinated currents, and to deduce therefrom faults selected from the group consisting of line breaks and short circuits at one or more of said first, second, or third terminals.

A method of diagnosing an exhaust-gas sensor for an internal combustion engine, the method comprising:

• providing a device with:
• a first terminal for connecting to a first electrode of a first cell of the exhaust-gas sensor;
• a second terminal for connecting to a second electrode of a second cell of the exhaust-gas sensor;
• a third terminal for connecting to a node between a second electrode of the first cell and a first electrode of the second cell of the exhaust-gas sensor;
• a first power source coupled to the first terminal in order to generate a first current and to apply the first current to the first cell;
• a second power source coupled to the second terminal in order to generate a second current and to apply the second current to the second cell;
• and
• a diagnostic means;
• controlling the first and second power sources in a coordinated fashion in order to generate the first and second currents as coordinated currents with respectively predefined signs;
• and
• determining one or more of the first, second, and third voltages when the respective first and second currents are present at the first, second, and/or third terminals and relating absolute values of the voltages to the coordinated currents in order to detect line breaks and/or short circuits at one or more of the first, second, or third terminals.