Method and device for monitoring a secondary air supply in an internal combustion engine

A diagnostic system for a secondary air supply in an internal combustion engine, wherein the internal combustion engine comprises:

• the secondary air supply configured to supply secondary air;
• a device configured to determine a pressure in the secondary air supply;
• an exhaust gas lambda probe configured to determine a current exhaust gas lambda value;
• and
• an evaluation device configured to:
• a) determine a first secondary air mass flow in relation to an effective throttle area using a throttle equation and according to the pressure in the secondary air supply;
• b) determine a second secondary air mass flow based on a measured exhaust gas lambda value and taking into account a primary air mass flow of the internal combustion engine and a supplied fuel mass flow;
• c) derive the effective throttle area from the first secondary air mass flow determined in step a) and the second secondary air mass flow determined in step b);
• and
• d) monitor the effective throttle area derived in step c) using at least one specified threshold value.

An exhaust system of an internal combustion engine, comprising:

• a diagnostic system for a secondary air supply in an internal combustion engine, wherein the internal combustion engine includes:
• the secondary air supply configured to supply secondary air;
• a device configured to determine a pressure in the secondary air supply;
• an exhaust gas lambda probe configured to determine a current exhaust gas lambda value;
• and
• an evaluation device configured to:
• a) determine a first secondary air mass flow in relation to an effective throttle area using a throttle equation and according to the pressure in the secondary air supply;
• b) determine a second secondary air mass flow based on a measured exhaust gas lambda value and taking into account a primary air mass flow of the internal combustion engine and a supplied fuel mass flow;
• c) derive the effective throttle area from the first secondary air mass flow determined in step a) and the second secondary air mass flow determined in step b);
• and
• d) monitor the effective throttle area derived in step c) using at least one specified threshold value.

A non-transitory machine-readable storage medium on which store stored commands for monitoring a secondary air supply in an internal combustion engine, wherein the internal combustion engine includes the secondary air supply, a device configured to determine a pressure in the secondary air supply, and an exhaust gas lambda probe configured to determine a current exhaust gas lambda value, the commands, when executed by at least one data processor, causing the at least one data processor to perform the following steps:

• a) determining, using a throttle equation and according to a pressure in the secondary air supply, a first secondary air mass flow in relation to an effective throttle area;
• b) determining a second secondary air mass flow based on a measured exhaust gas lambda value and taking into account a primary air mass flow of the internal combustion engine and a supplied fuel mass flow;
• c) deriving the effective throttle area from the first secondary air mass flow determined in step a) and the second secondary air mass flow determined in step b);
• and
• d) monitoring the effective throttle area derived in step c) using at least one specified threshold value.