Method for operating an internal combustion engine

1. A method for operating an internal combustion engine having probe measuring a gas concentration of a gas mixture, said probe comprising a pump electrode, the method comprising:

controlling a first pump current at the pump electrode to provide a resulting first pump voltage;

controlling a second pump current at the pump electrode to provide a resulting second pump voltage, wherein the second pump voltage is greater than the first pump voltage;

calculating an aging factor for the probe on the basis of the first pump current and the second pump current;

following the control of the first pump current and second pump current, controlling a third pump current to provide the first pump voltage; and

adapting operation of the internal combustion engine based on a characteristic of the probe corresponding to the calculated aging factor only if the third pump current deviates from the first pump current by less than a predetermined threshold.

2. The method as claimed in claim 1 , wherein the second pump voltage is high enough to decompose water contained in the gas mixture into oxygen and hydrogen.

3. The method as claimed in claim 1 , wherein the first pump voltage is not high enough to decompose water contained in the gas mixture into oxygen and hydrogen.

4. The method as claimed in claim 1 , wherein calculating the aging factor includes using the formula:

a =(( IP 2− IP 1)/C_(H_2 O )+ IP 1/C_(O_2))/0.21

where:

a is the aging factor of the probe,

IP1 is the first pump current,

IP2 is the second pump current,

C_(H_2 O) is a proportionality factor between a water concentration and the pump current, and

C_(O_2) is a proportionality factor between an oxygen concentration and the pump current.

5. The method as claimed in claim 1 , wherein the predetermined threshold is approximately 5% of the first pump current.

6. The method as claimed in claim 1 , further comprising filtering the aging factor with a low-pass filter to determine a filtered aging factor.

7. The method as claimed in claim 6 , further comprising identifying the probe as faulty if the filtered aging factor drops below a predetermined aging threshold.

8. The method as claimed in claim 1 , wherein the method is implemented during an overrun cut-off phase of the internal combustion engine.

9. The method as claimed in claim 1 , further comprising implementing the method independently of an air composition in relation to a water vapor pressure and a reference vapor pressure.