Location
The CDI control unit (N3/33) is located in the engine compartment on the right.
S07.16-4637-06
Task
The CDI control unit (N3/33) operates in an electrical network of sensors and actuators to form the engine management system.
According to the input signals, the following systems and functions, among other things, are controlled and coordinated:
Fuel supply
Control of glow system
Injection quantity control
Diagnosis and fault storage
Heat management
Exhaust gas recirculation
Exhaust treatment
ECO start/stop function (with CODE MJ8 (ECO start/stop function))
The CDI control unit (N3/33) has an internal atmospheric pressure sensor.
Input and output signals
The CDI control unit (N3/33) evaluates the following input signals and issues the appropriate output signals:
Direct input and output signals
CAN signals
Direct input signals
The CDI control unit (N3/33) reads in the signals from the following component parts:
Hot film mass air flow sensor (B2/8)
Rail pressure sensor (B4/14)
Low-pressure exhaust gas turbocharger boost pressure sensor (B5/9)
Camshaft Hall sensor (B6/23)
Coolant temperature sensor (B11/17)
Refrigerant pressure sensor (B12)
Low pressure exhaust gas recirculation temperature sensor (B16/14) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor downstream of oxidation catalytic converter (B19/8) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of SCR catalytic converter (B16/12) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of the oxidation catalytic converter (B16/19) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor downstream of SCR catalytic converter (B16/27) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Charge air temperature sensor upstream of the throttle valve (B17) (without CODE MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Exhaust gas temperature sensor (B17/7) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of catalytic converter (B19/7) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of exhaust gas turbocharger (B19/11) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of the exhaust gas turbocharger (B19/2) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Temperature sensor upstream of the diesel particulate filter (B19/17) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Pressure sensor downstream of throttle valve (B28/7) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Diesel particulate filter differential pressure sensor (B28/12)
NOX sensor 1 upstream of SCR catalytic converter (B29)
NOX sensor 2 downstream of SCR catalytic converter (B29/1)
Accelerator pedal module (B37/4)
Fuel temperature sensor (B50/5)
Exhaust back pressure sensor (B60/3)
Crankshaft Hall sensor (B70/2)
Fuel filter condensation sensor (B76)
Soot particulate sensor (B163/2) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Sensor unit for temperature sensors (B175) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Lambda sensor upstream of catalytic converter (G3/2) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Brake light switch (S9/3)
Exhaust gas recirculation positioner (high-pressure circuit) (Y27/9)
Regulated oil pressure pump valve (Y133)
Clutch pedal switch (S40/3)
MJ8Clutch pedal switch (S40/6) with CODE () ECO start/stop function
Cruise control lever (S40/4)
Direct output signals
The CDI control unit (N3/33) directly actuates the following component parts:
Throttle valve actuator (M16/45)
Low temperature circuit 1 coolant pump (M75/16) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Low temperature circuit 2 coolant pump (M75/17) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Glow output stage (N14/8)
Coolant preheating heating module (N33/2) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Exhaust gas recirculation positioner (high-pressure circuit) (Y27/9)
Fuel injectors (Y76)
Exhaust gas turbocharger actuator (Y77/2) (with code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Boost pressure control pressure transducer (Y77/11) (without code MT2 (emissions class Euro 6d-TEMP N1 GR.III/N2))
Quantity control valve (Y94/3)
CAN signals
To do this the CDI control unit (N3/33) communicates via the vehicle CAN (CAN V) with the following control units:
Instrument cluster (IC) control unit (A1/1) via the central gateway (CGW) (N93) and user interface CAN (CAN HMI)
Supplemental restraint system control unit (SRS) (N2/18),
Signal acquisition and actuation module (SAM) control unit (N10/1)
Climate control control unit (N154)
Electronic Stability Program control unit (ESP) (N30/4)
Fuse and relay module (SRM) control unit (N50)
Steering column tube module (MRM) control unit (N80) via the central gateway (CGW) (N93) and suspension CAN (CAN E)
Glow system control
The CDI actuates the glow output stage (N14/8) directly via the CDI control unit (N3/33) . This in turn actuates the glow plugs (R9):
Cylinder 1 glow plug (R9/1)
Cylinder 2 glow plug (R9/2)
Cylinder 3 glow plug (R9/3)
Cylinder 4 glow plug (R9/4)
A distinction is made between "preglowing", "start-up glowing" and "afterglowing".
Fuel supply
The CDI control unit (N3/33) actuates the fuel pump with fill level sensor (M3/3) via the fuel system control unit (FSCU) (N118), which delivers the fuel to the high-pressure pump via the fuel filter. The quantity control valve (Y94/3) regulates the feed to the high-pressure pump according to the actuation by the CDI control unit (N3/33) . The fuel pressure is regulated in the high-pressure pump to about 4.0 bar.
The quantity control valve (Y94/3) regulates the feed of fuel to the high-pressure pump according to the actuation by the CDI control unit (N3/33) in order to keep the temperature of the fuel low. The fuel temperature is detected via the fuel temperature sensor (B50/5) and transmitted permanently to the CDI control unit (N3/33). Any fuel not required flows back into the fuel tank through the return line.
Injection quantity control
The high-pressure pump pushes the fuel with an increased pressure in the common rail which distributes the fuel to the fuel injectors (Y76). The "common rail" literally means "common line". The fuel upstream of the injection is stored in this common line. The CDI control unit (N3/33) actuates the fuel injectors (Y76) depending on rotational speed and load:
Cylinder 1 injector (Y76/9)
Cylinder 2 injector (Y76/10)
Cylinder 3 injector (Y76/11)
Cylinder 4 injector (Y76/12)
A distinction is made between "preinjection", "main injection" and "post injection" in the corresponding driving situations. The system's maximum injection pressure is 1600 bar.
Structure
The housing of the CDI control unit (N3/33) is made out of diecast aluminum and the cover is made out of corrosion-proof sheet steel. The CDI control unit (N3/33) is water proof and dust proof.
Ground connection
The "circuit 31" ground connection is made via multiple ground lines to the right engine compartment ground point (W2/2).
Variants
The engine management variants, such as the country and exhaust variants, are activated via the variant coding; the CDI control unit (N3/33) does not have to be replaced for this.