Process for checking a burner system for heating a catalytic converter

A process for checking the ability to function of a burner being disposed in an exhaust pipe of an internal combustion engine and being operated with a fuel/air mixture for heating up an exhaust-gas catalytic converter of the internal combustion engine, which comprises:

• placing first and second lambda probes respectively upstream and downstream of the exhaust-gas catalytic converter;
• emitting output signals from each of the lambda probes corresponding to a respective residual oxygen content in the exhaust gas;
• representing rich and lean mixture compositions with signal levels of the output signal;
• detecting the signal levels of output voltages of both of the lambda probes;
• selectively enriching and diluting the fuel/air mixture of the internal combustion engine at a function of the signal levels by enrichment and dilution factors until both lambda probes change their signal levels;
• detecting values then occurring for the enrichment and dilution factors;
• determining an air ratio of the burner from the values for the enrichment and dilution factors and from air masses fed to the burner and the internal combustion engine during checking;
• and
• comparing the air ratio of the burner with predetermined limiting values, and classifying the burner as currently not capable of operating properly if the air ratio of the burner is outside the limiting values.