Method and device for controlling and/or monitoring the function of a secondary air supply in an emission control system

An emission control system of an internal combustion engine, the emission control system comprising:

• an engine control unit that includes a least one of a storage device and a comparator unit;
• and
• in a central section of the emission control system:
• a first catalytic converter situated in an exhaust duct;
• a second catalytic converter situated in the exhaust duct in sequence with the first catalytic converter;
• a lambda probe that is situated, with respect to a direction of flow of exhaust gas, downstream of an engine block and upstream of the first catalytic converter and that is configured to supply signals to the engine control unit;
• an exhaust-gas probe that is downstream of the first catalytic converter and of the second catalytic converter;
• a secondary air supply configured to introduce air between the first and second catalytic converters for optimized operation of the second catalytic converter;
• and
• a two-point lambda probe that is situated downstream of the first catalytic converter and of the secondary air supply and is configured to supply signals to the engine control unit;
• wherein the engine control unit is configured to:
• perform a catalytic converter diagnosis;
• use the signals from the two-point lambda probe to perform at least one of a secondary air diagnosis and a secondary air control of the secondary air supply;
• and
• apply to the two-point lambda probe measures that compensate tolerance and aging effects of the two-point lambda probe.