Operating strategy and display concept for US diesel

BMW US diesel vehicles with SCR system can only be operated (driven) when the SCR system is operational. In order to establish operational status, there must be sufficient urea/water mixture in the corresponding tanks. This tank system is divided into an active tank and a passive tank. The vehicle tanks are filled via the corresponding service hatches. There is a service hatch for the active tank and a separate opening for the passive tank. In general, the mixture that is metered directly into the exhaust tract is taken exclusively from the active tank. The active tank is heated. The passive tank is not heated. There is a pump device to deliver the urea/water mixture from the passive tank into the active tank. On a longer journey, to ensure continuous vehicle readiness, the mixture must neither age to any great extent nor freeze. Important note: If the SCR system cannot be operated, the vehicle cannot be operated! The customer must be informed of the necessity to fill the system with the urea/water mixture.

As soon as the mixture stored in the vehicle reaches a critical fluid level, an acoustic signal sounds and the remaining range is displayed in the indicating instrument of the vehicle. Reaching of a critical fluid level in the active tank can be read out by querying the tank volume in the control unit function "mixture fluid level active tank" or "total remaining tank volume".

Important note: If the critical fluid level of the active tank is reached, the vehicle enters an automatic shutdown scenario. The customer must be made aware of the fact that this shutdown scenario can be prevented by topping up the active tank with new urea/water mixture! (In this situation, topping up the passive tank has only a limited effect!)