CDI driving mode, function

General function requirements

 Circuit 61 ON

 Engine running

 Vehicle in motion

Common rail diesel injection (CDI) driving mode - general

The basic tasks of the CDI in automotive operation include providing an engine torque which matches the driver's requirements. At the same time, the CDI should provide for ideal smooth running characteristics at the lowest possible fuel consumption and minimal exhaust emissions. To do this, the CDI control unit (N3/9) must adjust the CDI and the air and exhaust system to one another according to the stored performance map data.

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For this purpose, the CDI control unit evaluates the following sensor information:

- Intake air volume and temperature, from the hot film MAF sensor (B2/5) with integrated intake air temperature sensor (B2/5b1)

- Rail pressure sensor (B4/6)

- Charge pressure sensor (B5/1)

- Coolant temperature sensor (B11/4)

Hot gas AGR temperature sensor (B16/14) (as of J10 except code (U41) Fuel/water separator and lubrication package and with code (928) Exhaust treatment with EU5 technology)

- Charge air temperature sensor (B17/8)

- Accelerator pedal sensor (B37), for the driver request

- Fuel temperature, through the fuel temperature sensor (B50)

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- Crankshaft position sensor (L5), for the engine speed

- O2 sensor downstream of CAT (G3/1) (as ofJ10 except code (U41) Fuel/water separator and lubricating package and with code (928) Exhaust treatment with EU5 technology), for the residual oxygen content in the exhaust

- O2-Probe upstream of CAT (G3/2) (up to ÄJ10 and except code (474) Particulate filter or with code (U41) Fuel/water separator and lubricating package), for residual oxygen content in exhaust

- Pressure differential sensor (DPF) (B28/8), with code (474) particulate filter

- Temperature sensor downstream of CAT (B19/8), with code (474) Particulate filter

- Temperature sensor upstream of turbocharger (B19/11), with code (474) Particulate filter

- Temperature sensor upstream of diesel particulate filter (B19/9) for code (474) Particulate filter

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The CDI control unit also controls the following components:

- Exhaust gas recirculation positioner (Y27/9) (up to ÄJ10 and with code (474) Particulate filter )

- Boost pressure control pressure transducer (Y31/5) (up to ÄJ10 or with code (U41) Fuel/water separator and lubricating package)

- Pressure transducer EGR/throttle valve (Y31/13) (up to ÄJ10 and except code (474) Particulate filter or with code (U41) Fuel/water separator and lubricating package)

AGR pressure transducer (Y31/14) (as of J10 except code (U41) Fuel/water separator and lubrication package and with code (928) Exhaust treatment with EU5 technology)

Hot gas AGR pressure transducer (Y31/15) (as of J10 except code (U41) Fuel/water separator and lubrication package and with code (928) Exhaust treatment with EU5 technology)

- Boost pressure regulator (Y100/2) (as ofJ10 except code (U41) Fuel/water separator and lubrication package and with code (928) Exhaust treatment with EU5 technology)

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The CDI control unit is connected to the following components via the drive LIN (LIN-C1):

- Alternator (G2)

- Glow time output stage (N14/3), glow function control

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

- With instrument cluster (A1), winter tire maximum speed, dynamometer test mode for electronic stability program (ESP)

- ESP and BAS control unit (N47-5), for example for ESP torque requests, wheel speeds

- EIS control unit (N73), interface with the interior CAN (CAN B), e.g. for switching status of the air conditioning system

- Electronic selector lever module control unit (N15/5), selector lever position "P" or "N", with transmission 722.8

- CVT control unit (continuously variable automatic transmission) (Y3/9n1), actual gear engaged, with transmission 722.8

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When driving, the following function sequences are active; they are described in separate documents:

 Fuel supply

 Injection control

 Quantity control

 Quantity mean value adaptation

 Zero quantity calibration

 Sliding operation

 Preheating

 Engine torque request

 Heat management

 Alternator interface

 Intake port shutoff

 Charging

 Exhaust gas recirculation

 Emission control

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 The engine speed is governed to approx. 4500 rpm. This counteracts mechanical damage to the engine caused by overrevving. Above an engine speed of around 4500 rpm, the CDI control unit interrupts actuation of the fuel injectors (Y76) and reduces the fuel pressure in the rail via the quantity control valve (Y94) and the pressure control valve (Y74).