CDI driving mode, function

The basic tasks of Common-Rail Diesel Injection (CDI) in driving mode include the provision of an engine torque, which corresponds to the accelerator pedal position. At the same time, optimum smooth running characteristics with low fuel consumption and low exhaust gas emissions are also required. To do this, the CDI control unit (N3/21) must adjust the CDI and the air and exhaust system to one another according to the stored performance map data.

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When the vehicle is in operation, the CDI controls the following functions via the CDI control unit (these functions are described in separate documents):

 Quantity control

 Charging

 Emission control, with code (MS9) Engine version Euro 4 or with code (MF4) Low-emission engine according to EU4 Group 3

 Shutoff of refrigerant compressor (A9), with code (HH9) Regulated air conditioning, (Tempmatic), with code (HH7) Additional air conditioning system in rear

 Shutoff of 2nd refrigerant compressor (A9/7), with code (H08) High-performance air conditioning system

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To do this, the CDI control unit reads the following parameters from the associated components:

- Current rail pressure via the rail pressure sensor (B4/6).

- Current boost pressure via the boost pressure sensor (B5/1), intake manifold pressure sensor (B28) and charge air temperature sensor (B17/9).

- Coolant temperature via the coolant temperature sensor (B11)

- Accelerator pedal position via the accelerator pedal module (B37/3).

- Fuel temperature via the fuel temperature sensor (B50).

- Exhaust back pressure via the exhaust back pressure sensor (B60).

- Engine speed via the crankshaft sensor (L5/7).

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On vehicles with code (MF4) Low-emission engine conforming to EU4 group 3 or with code (MS9) Engine version Euro 4, the CDI control unit also reads in the following variables from the associated components:

- Temperature upstream of the near-engine mounted catalytic converter via the catalytic converter temperature sensor (B19).

- Intake air mass and its temperature via the hot film mass air flow sensor (B2/5) and integrated intake air temperature sensor (B2/5b1).

- Temperature upstream of the diesel particulate filter (DPF) via the temperature sensor upstream of the diesel particulate filter (B19/12).

- Exhaust pressure upstream and downstream of the DPF via the diesel particulate filter differential pressure sensor (B28/8).

- Residual oxygen content in the exhaust gas via the oxygen sensor (B85).

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In addition, the CDI control unit communicates with the following control units via the Control Area Network bus Class C (engine compartment) (CAN-C) to obtain information on further variables:

- With the instrument cluster (A1) as an interface to the Controller Area Network bus Class B (interior) (CAN-B) in order to process, for example, a set winter tire maximum speed.

- On vehicles with transmission 722.6: with the ETC [EGS] control unit (N15/3) in order to obtain, for example, information about the actual gear engaged.

- On vehicles with transmission 722.6: with the ESM [EWM] control unit (N15/5) in order to obtain, for example, information about the selector lever position "P" or "N".

- With the ESP control unit (N30/4) in order to obtain, for example, the wheel speeds of the wheels.

- With the EIS [EZS] control unit (N73) as an interface to CAN-B in order to obtain, for example, the switching status of the air conditioning system on vehicle with code (HH9) Regulated air conditioning, (Tempmatic).