CDI start quantity control, function

Start quantity control is used during engine start to calculate a specific start quantity independently of the position of the accelerator pedal sensor (B37) if the coolant temperature is < 80°C and if the engine speed is < 500 rpm. The CDI control unit (N3/9) reads in the following information via the Controller Area Network bus Class C (engine compartment) (CAN-C) to do this:

 The position of the accelerator pedal sensor

 The selector lever position "P" or "N", from the Electronic Selector Lever Module control unit (N15/5)

 The message "DAS 3 Message MS" and the message "Circuit 50 ON", from the EIS control unit (N73)

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Via a discrete line:

 Coolant temperature from the coolant temperature sensor (B11/4)

 Engine speed from the crankshaft position sensor (L5)

The CDI control unit uses the input signals to calculate the respective start quantity and controls the following components accordingly:

 Pressure regulator valve (Y74)

 Cylinder 1 fuel injector (Y76y1)

 Cylinder 2 fuel injector (Y76y2)

 Cylinder 3 fuel injector (Y76y3)

 Cylinder 4 fuel injector (Y76y4)

 Quantity control valve (Y94)

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If the CDI control unit detects that the engine is running via the crankshaft position sensor and the message "Circuit 61 ON" and that the starting procedure has ended via the message "Circuit 50 ON", then the driver can influence the injection quantity and thus the engine speed via the accelerator pedal sensor.