CDI driving mode, function

The basic tasks of Common-Rail Diesel Injection (CDI) in driving mode include 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 emissions are also required. To do this, the CDI control unit (N3/21) must adjust the CDI as well as the air and exhaust system to one another according to the stored performance map data.

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

– the current rail pressure, via the fuel pressure sensor (B4/6)

– the current boost pressure, via the boost pressure sensor (B5/1), the intake manifold pressure sensor (B28/11) and the charge air temperature sensor (B17/9)

- the coolant temperature, over the coolant temperature sensor (B11)

– the accelerator pedal position, over the accelerator pedal module (B37/3)

– the fuel temperature, over the fuel temperature sensor (B50)

– the exhaust back pressure, over the exhaust back pressure sensor (B60)

- the engine speed, over the crankshaft position sensor (L5/7)

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

- the intaken air mass and its temperature via the hot film MAF sensor (B2/5) and the integrated intake air temperature sensor

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

– the exhaust pressure upstream and downstream of the DPF, via the diesel particulate filter differential pressure sensor (B28/8)

– the residual oxygen content in exhaust, via the oxygen sensor (B85/2)

The CDI control unit also communicates with the following control units via the engine compartment CAN (CAN C), to obtain the related variables:

– with the climate control control and operating unit (A81) (for vehicles with code (HH9) Regulated air conditioning, (Tempmatic)), in order, for example, to obtain the switching condition of the A/C compressor (Y38)

– with the ESP control unit® (N30/4), in order, for example, to obtain the wheel speeds of the wheels

– with the IC (P15), in order, for example, to adopt the outside temperature from the outside temperature sensor (B37)

When driving, the CDI controls the following functions over the CDI control unit, which are described in further documents:

 Quantity control

 Shutoff of the A/C compressor, with code (HH9) Regulated air conditioning, (Tempmatic)

 Engine speed

 Charging

 Exhaust gas recirculation

 Exhaust treatment