Patent ID: 7484407

Claim:
A method for diagnosis of an exhaust gas cleaning system incorporated in an exhaust tract of an internal combustion engine having a first exhaust manifold a second exhaust manifold and includes a first individual catalytic converter associated with the first exhaust manifold and a second individual catalytic converter associated with the second exhaust manifold, the exhaust pipes of the first and second manifolds converge into a common exhaust pipe downstream of the two individual catalytic converters, a main catalytic converter located downstream of the common exhaust pipe, an exhaust gas probe arranged upstream of the first individual catalytic converter, an exhaust gas probe arranged upstream of the second individual catalytic converter, an exhaust gas probe arranged between the first individual catalytic converter and the main catalytic converter, and an exhaust gas probe arranged downstream of the main catalytic converter, comprising: determining an oxygen storage capacity of the first individual catalytic converter based on signals of the exhaust gas probe upstream of the first individual catalytic converter and signals of the exhaust gas probe between the first individual catalytic converter and the main catalytic converter; determining a sum of the oxygen storage capacities of the first individual catalytic converter and main catalytic converter based on signals of the exhaust gas probe upstream of the first individual catalytic converter and signals of the exhaust gas probe downstream of the main catalytic converter; determining a sum of the oxygen storage capacities of the second catalytic converter and the main catalytic converter based on signals of the exhaust gas probe upstream of the second individual catalytic converter and signals of the exhaust gas probe downstream of the main catalytic converter; and determining an oxygen storage capacity of the second individual catalytic converter based on the oxygen storage capacity of the first individual catalytic converter, the sum of the oxygen storage capacities of the first individual catalytic converter and the main catalytic converter, and the sum of the oxygen storage capacities of the second individual catalytic converter and the main catalytic converter.