Exhaust Gas Recirculation (EGR)

During normal operation, the exhaust gas recirculation is controlled based on the EGR ratio. During regeneration of the diesel particulate filter, it is conventionally controlled based on the air mass.

The monitoring function also differs in this way: During normal operation a fault is detected when the EGR ratio is above or below defined limits for a certain period of time.

This applies to the air mass during regeneration of the diesel particulate filter. In order to monitor the high pressure EGR cooler, the temperature after the high pressure EGR cooler is measured with the bypass valve open and close with the engine running at idle speed. A fault is detected if the temperature difference is below a certain value.

For the low pressure EGR cooler (only E70), the measured temperature after the low pressure EGR cooler is compared with a calculate temperature for this position. A fault is detected if the difference exceeds a certain value.

Each of these faults is stored reversible. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated.