摘要 |
An emission control system is monitored by measuring time periods during which the signal of a post-catalyst lambda probe lies below or above an engine speed/load dependent threshold value. The measurements are weighted with an engine speed/load dependent value and subsequently summed so that a total reference time period, which constitutes a measure of the additionally emitted pollutants, can be related to the overall operating time period. If the ratio exceeds a predefined value, a faulty function of the pre-catalyst lambda probe is diagnosed. The method permits the onboard diagnosis of the lambda control of the catalytic emission treatment system.
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