CDI start quantity control, function

At engine start, start control calculates the fuel start quantity independently of the position of the accelerator pedal module (B37/3), but in line with the coolant temperature (at < 80°C) and engine speed (at < 500 rpm).

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For this step, the CDI control unit (N3/21) reads in the following messages and signals from the components:

- Message "DAS 3 Message MS" and message "Circuit 50 ON" from the EIS [EZS] control unit (N73) via the Controller Area Network bus Class C (engine compartment) (CAN-C)

- Coolant temperature from the coolant temperature sensor (B11) via a discrete line

- Position of the accelerator pedal module via CAN-C

- Engine speed from the crankshaft sensor (L5/7) via a discrete line

- On vehicles with transmission 722.6: selector lever position "P" or "N" message from the ESM [EWM] control unit (N15/5) via CAN-C

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Using the input signals, the CDI control unit calculates the respective fuel start quantity and then actuates the following components:

- Pressure regulator valve (Y74)

- Cylinder 1 injector (Y76/1)

- Cylinder 2 injector (Y76/2)

- Cylinder 3 injector (Y76/3)

- Cylinder 4 injector (Y76/4)

- Quantity control valve (Y94)

If the CDI control unit detects that the engine is running via the crankshaft sensor and the message "circuit 61 ON", and that the starting procedure has ended via the message "circuit 50 OFF", the driver can adjust the injection quantity using the accelerator pedal module and thus change the engine speed.