Patent ID: 7343734

Claim:
A method for adjusting a defined oxygen concentration by means of binary lambda regulation in order to diagnose a catalyst whereby regulation of the catalyst results in control cycles, the method comprising the following steps: catalyst diagnosis is carried out at a predetermined defined oxygen concentration for each control cycle, a fuel mixture can be adjusted to rich or lean according to a lambda control factor, a rich or lean exhaust gas is detected, in the case of a lean exhaust gas, the lambda control factor is increased incrementally, in the case of a rich exhaust gas the lambda control factor is decreased incrementally, after a change has been detected from a rich exhaust gas to a lean exhaust gas or from a lean exhaust gas to a rich exhaust gas, the lambda control value is changed by a P step, after a change has been detected from a rich exhaust gas to a lean exhaust gas the lambda control factor is set during a first loading time to a minimum control factor value, which represents a local minimum for the control factor value in the current control cycle, and after a change has been detected from a lean exhaust gas to a rich exhaust gas the lambda control factor is set during a second loading time to a maximum control factor value, which represents a local maximum for the control factor value in the current control cycle, whereby the first loading time is adjusted so that the oxygen concentration achieves an oxygen input defined by the predetermined oxygen concentration in each control cycle, and whereby the second loading time is adjusted so that the oxygen concentration achieves an oxygen output defined by the predetermined oxygen concentration in each control cycle.