Preheating system N47TU, N57TU: Function

The required glow plug temperature is determined by the DDE control unit on the basis of the following operating values:

• Coolant temperature
• Engine speed
• Intake air temperature
• Injection rate
• Ambient pressure
• On-board voltage
• Status signal for starter enable

To activate glowing, the DDE sends the required glow plug temperature to the combustion preheating control unit. Across the LIN bus, the DDE also sends the following operating values to the preheating control unit:

• Coolant temperature
• Intake air temperature
• Ambient pressure
• On-board voltage
• Injection rate
• Engine speed
• Status signal for starter enable

The preheating control unit uses these three operating values to determine the required current for the heater plugs and supplies the heater plugs with current.

• N47 in MINI:  The preheating control unit has only two output stages for activating the four heater plugs. The heater plugs of cylinders 1 and 2 are energized by one output stage and the heater plugs of cylinders 3 and 4 are energized by the other output stage. In diagnosis this results in the fault codes of both heater plugs of one output stage being stored in the event of a fault in the heater plug activation system.
• N47 in BMW:  The preheating control unit has four output stages for activating the four heater plugs. Each heater plug is energized by its own output stage.