Abstract: 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.

Abstract: A method for monitoring a subsystem installed in a motor vehicle involves a diagnostic unit checking the subsystem for system errors at least during driving cycles of the motor vehicle, the check being carried out for an occurrence as well as for a correction of a system error. The diagnostic unit carries out a misuse assessment based on a frequency of detection of the occurrence and/or the correction of the system error in order to determine whether the detected occurrence and/or the detected correction of the system error is/are based on misuse. If occurrence of the system error is detected, a restricted operating mode is activated or an activated restricted operating mode is continued in which drivability of the vehicle is restricted after a predefinable number of driving cycles has elapsed or after a predefinable travel distance has passed without the correction of the system error being detected.

Abstract: A method for monitoring a subsystem installed in a motor vehicle involves a diagnostic unit checking the subsystem for system errors at least during driving cycles of the motor vehicle, the check being carried out for an occurrence as well as for a correction of a system error. The diagnostic unit carries out a misuse assessment based on a frequency of detection of the occurrence and/or the correction of the system error in order to determine whether the detected occurrence and/or the detected correction of the system error is/are based on misuse. If occurrence of the system error is detected, a restricted operating mode is activated or an activated restricted operating mode is continued in which drivability of the vehicle is restricted after a predefinable number of driving cycles has elapsed or after a predefinable travel distance has passed without the correction of the system error being detected.