Daimler Ag

Mercedes-benz Group Ag

Rainer Hegemann

Markus Paule

Norbert Waldbuesser

Herbert Schankula

Eugen Neuberger

Nhat Phan

Matthias Hoelz

Yvonne Binder

Norbert WALDBÜSSER

A method for operating a nitrogen oxide sensor of an internal combustion engine. When, for a number greater than 1 of operating cycles each including exactly two directly consecutive periods of time, where during a respective first of the periods of time the engine is in fired operation and during the respective second period of time a fired operation of the engine ceases, it is determined that an arithmetic mean of the first periods of time is less than a first threshold value and an arithmetic mean of the second periods of time is less than a second threshold value, a special overrun operating state of a computer is set, where after deactivation of the engine, the computer is kept activated in the special overrun operating state for a longer overrun period, where the nitrogen oxide sensor is kept in a state of operating readiness during the overrun period.

Method for operating a nitrogen oxide sensor

A method for operating an exhaust gas purification system of a motor vehicle internal combustion engine is disclosed. The system has an SCR catalyst where a reducing agent containing ammonia is metered into the exhaust gas at a predeterminable metering rate which is produced from a base value and an adaptation factor which corrects the base value. A test procedure checks and, if appropriate, adjusts the adaptation factor where a first nitrogen oxide value is compared with a second nitrogen oxide value of the exhaust gas, where the first and the second nitrogen oxide value are determined by the same nitrogen oxide sensor disposed downstream of the SCR catalyst. The first nitrogen oxide value is determined when the metering of the reducing agent is switched off and the second nitrogen oxide value is determined when the reducing agent is metered at a test metering rate which can be predetermined.

Method for operating an exhaust gas purification system of a motor vehicle combustion engine

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Ludwigsburg, Germany

Rainer Hegemann