Device and method for determining an offset in a signal of a sensor for measuring residual oxygen

A method for correcting an offset in a signal of a first sensor configured to determine a residual oxygen content in an exhaust gas, the method comprising the following steps:

• predetermining a reference ratio of air and fuel is for an output of a catalytic converter;
• measuring, by the first sensor, a first residual oxygen content in the exhaust gas upstream of the catalytic converter;
• determining a first actual ratio of air and fuel as a function of the first residual oxygen content;
• measuring a second residual oxygen content in the exhaust gas downstream of the catalytic converter by a second sensor which is configured to determine residual oxygen content in the exhaust gas;
• determining a second actual ratio of air and fuel as a function of the second residual oxygen content;
• determining a first offset of a first actual ratio relative to the reference ratio for the first actual ratio when the second actual ratio is greater than the reference ratio;
• determining a second offset of a first actual ratio relative to the reference ratio for the first actual ratio when the second actual ratio is smaller than the reference ratio;
• and
• detecting a deviation between the first offset and the second offset.