Method and arrangement for monitoring a lambda probe in an internal combustion engine

A method for monitoring first and second lambda probes in the context of a two-probe closed-loop control, the first and second lambda probes being arranged forward and rearward of a catalytic converter, respectively, the method comprising the steps of:

• utilizing the signal of the first probe arranged forward of the catalytic converter to serve for lambda control;
• utilizing the signal of the second probe rearward of the catalytic converter to influence the lambda controller by means of an actuating variable;
• utilizing the degree of the influence to monitor said first probe;
• comparing the signal of said second probe to a threshold value;
• integrating the comparison signal;
• utilizing the integrated signal for influencing the lambda controller;
• monitoring the actuating variable as to at least one of a lower limit and an upper limit when selectable operating conditions are present;
• and,
• when there is a drop below the lower limit or the upper limit is exceeded, generating a fault announcement.