View of engine from top front |
B4/6 | High-pressure fuel pressure sensor |
B6/1 | Camshaft Hall sensor |
B11/4 | Coolant temperature sensor |
R9/1 | Cylinder 1 glow plug |
R9/2 | Cylinder 2 glow plug |
R9/3 | Cylinder 3 glow plug |
R9/4 | Cylinder 4 glow plug |
R9/5 | Cylinder 5 glow plug |
R9/6 | Cylinder 6 glow plug |
Y27/9 | Exhaust gas recirculation positioner (high-pressure circuit) |
Y74 | Pressure regulator valve |
Y77/1 | Boost pressure control pressure transducer |
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Location
The CDI control unit (N3/28) is located centrally on the engine.
Task
The CDI control unit performs the following tasks:
Controlling the engine basic functions
Reading in of signals
Evaluation of input factors
Output of signals and actuation of components
Apart from this, the CDI control unit serves as an interface between the connected CAN bus systems.
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Block diagram of direct signals to the CDI control unit |
B1 | Engine oil temperature sensor | B70 | Crankshaft Hall sensor | |
B2/6 | Left hot film MAF sensor | K1/7 | Circuit 87M relay | |
B2/6b1 | Left intake air temperature sensor | G1 | On-board electrical system battery | |
B2/7 | Right hot film MAF sensor | G3/2 | Oxygen sensor upstream of catalytic converter | |
B2/7b1 | Right intake air temperature sensor | M1 | Starter | |
B4/6 | High-pressure fuel pressure sensor | M72/2 | Intake port shutoff actuator | |
B5/1 | Boost pressure sensor | M91 | Electric fan | |
B6/1 | Camshaft Hall sensor | M16/6 | Throttle valve actuator | |
B11/4 | Coolant temperature sensor | N3/28 | CDI control unit | |
B16/15 | Temperature sensor upstream of SCR catalytic converter | N50k1 | Starter relay | |
B17/8 | Charge air temperature sensor | R39/1 | Vent line heater element | |
B19/7 | Temperature sensor upstream of catalytic converter | S43 | Oil level check switch | |
B19/9 | Temperature sensor upstream of diesel particulate filter | Y27/9 | Exhaust gas recirculation positioner (high-pressure circuit) | |
B19/11 | Temperature sensor upstream of turbocharger | Y74 | Pressure regulator valve | |
B28/5 | Pressure sensor downstream of air filter | Y76 | Fuel injectors | |
B28/8 | Differential pressure sensor (DPF) | Y77/1 | Boost pressure control pressure transducer | |
B37/4 | Accelerator pedal module | Y85 | Exhaust gas recirculation cooler bypass switchover valve | |
B50 | Fuel temperature sensor | Y94 | Quantity control valve | |
B60 | Exhaust pressure sensor |
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Networking |
A1/1 | Instrument cluster (KI) control unit | N141 | AdBlue® (SCR) control unit | |
A97/1 | Control unit of NOx sensor upstream of SCR catalytic converter | N154 | Climate control control unit | |
A97/2 | NOx sensor control unit downstream of SCR catalytic converter | X11 | Diagnostic connector | |
G2 | Alternator | CAN C | Drive train CAN | |
N2/18 | Supplemental restraint system (SRS) control unit | CAN D | Diagnostic CAN | |
N3/28 | CDI control unit | CAN E | Chassis CAN | |
N14/8 | Glow output stage | CAN HMI | User interface CAN | |
N15/11 | Fully integrated transmission control (VGS) electric controller unit | CAN I | Drive train sensor CAN | |
N30/4 | Electronic Stability Program (ESP) control unit | CAN V | Vehicle CAN | |
N50 | Fuse and relay module control unit (SRM) | LIN C3 | Drivetrain LIN | |
N80 | Steering column tube module (MRM) control unit | A | Mercedes-Benz | |
N93 | Central gateway (CGW) | B | Nissan | |
N118 | Fuel system control unit (FSCU) | C | Default | |
N127 | Drivetrain control unit | D | Optional |
Common rail direct injection CDI, general
The CDI regulates the injection quantity in all operating statuses. The engine management takes place through the CDI control unit.
The engine management is subdivided into the following systems:
Engine system
Diesel injection system
Glow system control
Fuel supply
Injection quantity control
Air control system
Exhaust system
Engine system
Throttle valve control
Safety fuel shutoff
Transmission overload protection
Support of the Electronic Stability Program (ESP®)
Anti-jerk control
Glow time control
European On-Board Diagnosis (EOBD)
Variant coding
Torque coordination
Alternator interface
Load determination
Maximum vehicle speed limit
Diesel injection system
Pre, main and post injection
Idle speed control
Smooth running control
Limp-home function
A/C rpm increase
Inertia fuel shutoff
Rail pressure regulation
Fuel pump controlling
Fuel high-pressure pump controller
Altitude adaptation
Rpm limitation
Glow system control
The CDI actuates the glow output stage via the CDI control unit. 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)
Cylinder 5 glow plug (R9/5)
Cylinder 6 glow plug (R9/6)
One differentiates between preglowing, start-up glowing and afterglowing.
Fuel supply
The fuel system control unit (FSCU) (N118) actuates the fuel pump with fill level sensor (M3/3), which delivers fuel via the fuel filter to the high-pressure pump. Depending on the actuation by the CDI control unit, the quantity control valve (Y94) regulates the feed to the high-pressure pump at approx. 4.0 bar.
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 CDI control unit actuates the fuel injectors, rotational speed and load-dependent:
Cylinder 1 fuel injector (Y76/1)
Cylinder 2 fuel injector (Y76/2)
Cylinder 3 fuel injector (Y76/3)
Cylinder 4 fuel injector (Y76/4)
Cylinder 5 fuel injector (Y76/5)
Cylinder 6 fuel injector (Y76/6)
Differentiation is made between preinjection, main injection and post-injection. The system's maximum injection pressure is 1600 bar.
Air control system
Charge pressure control
Exhaust gas recirculation (EGR)
Intake air throttling through intake port shutoff (EKAS)
Exhaust system
Catalytic converter heating
Oxygen sensor heater
Exhaust gas cleaning, diesel particulate filter regeneration
Exhaust aftertreatment, injection of the reduction agent AdBlue®
Ignition ON, function | |||
Starting, function | |||
Ignition OFF, function | |||
Fuel supply, function | |||
Injection regulation, function | |||
Rpm control, function | |||
Alternator interface function | |||
Smooth running control, function | |||
Thermal management, function | |||
Torque coordination, function | |||
Overrun mode fuel shutoff, function | |||
Engine limp-home mode, function | |||
European OBD, function | |||
ECO start/stop function engine management, function | With CODE MJ8 (ECO start/stop function) | ||
Charging, function | |||
Exhaust gas recirculation, function | |||
Preheat, function | |||
Exhaust gas cleaning, function |