Networking with the Digital Diesel Electronics (DDE)

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The SCR control unit is connected to the DDE control unit via the powertrain CAN.

The Digital Diesel Electronics (DDE) sends the request with the calculated volume of AdBlue and the release to the SCR control unit via the powertrain CAN. AdBlue is metered depending on the load (flow rate and exhaust-gas temperature), the temperature profile and the load profile.

The DDE must ensure a sufficiently high exhaust-gas temperature and take measures where necessary to increase the exhaust-gas temperature. The NO_x conversion rates that can be achieved depend on the temperature in the SCR catalytic converter.

Two nitrogen oxide sensors are connected to the Digital Diesel Electronics (DDE).:

Nitrogen oxide sensor before SCR catalytic converter
Nitrogen oxide sensor after SCR catalytic converter

Each nitrogen oxide sensor is connected to the DDE control unit by a separate local CAN.

The nitrogen oxide sensors allow the DDE to evaluate the nitrogen oxide concentration before and after the SCR catalytic converter. This allows the effectiveness (chemical reaction of pollutants to normal elements in the air) of the SCR catalytic converter to be monitored.

A temperature sensor is integrated in the SCR catalytic converter. The temperature sensor is connected to the Digital Diesel Electronics. The DDE control unit uses it to monitor the temperature in the SCR catalytic converter.