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GCU
(Glow Plug Control Unit)
EGR Bypass ValveEGR Valve
Electric Throttle Body
Water Sensor
Variable Swirl Valve Actuator
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15-6
Fuel Rail Pressure SensorFront EGT Sensor
Differential Pressure SensorCamshaft Position SensorRear EGT Sensor
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Fuel Temperature
SensorCoolant Temperature Sensor
Knock Sensor (2)T-MAP SensorD20DTR ECU
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Fuel rail pressure Water sensor
(2) Components for ECU Input
CAN
- ABS & ESP
- GCU
- Indicator/
Warning Lamp,
Meter Cluster
- TCUSwirl valve
position
sensor
Differential
pressure sensorE-EGR valve
position
sensorCamshaft position
sensorCoolant
temperature
sensor
EGT sensorHFM sensorOxygen sensorT-MAP sensor
Crankshaft
position
sensorAccelerator pedal
sensorThrottle
position
sensorKnock sensor
- Auto cruise switch
- Refrigerant pressure
sensor
- Blower switch signal
- Brake pedal signal
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15-10
(3) Components for ECU Output
CAN
E-EGR cooler
bypass valve
- TCU
- Self diagnosis
Cooling fan
E-EGR valve
Variable swirl
valveE-VGT actuatorIMV valve
A/C
compressorInjectorThrottle position
sensor
- ABS & ESP unit
- GCU
- Indicator/Warning Lamp, Meter Cluster
PTC heater
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2) ECU Control
(1) Function
a. ECU Function
ECU receives and analyzes signals from various sensors and then modifies those signals into
permissible voltage levels and analyzes to control respective actuators.
ECU microprocessor calculates injection period and injection timing proper for engine piston speed
and crankshaft angle based on input data and stored specific map to control the engine power and
emission gas.
Output signal of the ECU microprocessor drives pressure control valve to control the rail pressure and
activates injector solenoid valve to control the fuel injection period and injection timing; so controls
various actuators in response to engine changes. Auxiliary function of ECU has adopted to reduce
emission gas, improve fuel economy and enhance safety, comforts and conveniences. For example,
there are EGR, booster pressure control, autocruise (export only) and immobilizer and adopted CAN
communication to exchange data among electrical systems (automatic T/M and brake system) in the
vehicle fluently. And Scanner can be used to diagnose vehicle status and defectives.
Operating temperature range of ECU is normally -40 to +85°C and protected from factors like
oil, water and electromagnetism and there should be no mechanical shocks.
To control the fuel volume precisely under repeated injections, high current should be applied instantly
so there is injector drive circuit in the ECU to generate necessary current during injector drive stages.
Current control circuit divides current applying time (injection time) into full-in-current-phase and hold-
current-phase and then the injectors should work very correctly under every working condition.
b. Control Function
Controls by operating stages
To make optimum combustion under every operating stage, ECU should calculate proper injection
volume in each stage by considering various factors.
Starting injection volume control
During initial starting, injecting fuel volume will be calculated by function of temperature and engine
cranking speed. Starting injection continues from when the ignition switch is turned to ignition
position to till the engine reaches to allowable minimum speed.
Driving mode control
If the vehicle runs normally, fuel injection volume will be calculated by accelerator pedal travel and
engine rpm and the drive map will be used to match the drivers inputs with optimum engine power. -
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MDP (Minimum Drive Pulse ) refers to the
minimum power supply pulse for injection which
the injector can perform. It is possible to control
the fuel volume for each injector accurately
through correct learning for the MDP value. The
basic process of MDP learning is that the pulse
slightly higher than MDP is supplied and then (b)
the vibration generated from the cylinder is
detected. The knock sensor detects the
vibration from the engine after a small volume of
fuel is injected. And the time interval between
the points of injection and vibration is measured
so that MDP can be learned. MDP learning is
helpful to prevent engine vibration, high
emission and power reduction through
performing calibration for the old injectors.
During MDP learning, a little vibration and noise
can be occur for a while. This is because the
fuel pressure is increased instantaneously and
the exact injection value is not input, so that the
exact engine vibration timing can be detected.
(6) MDP Learning Control
A. MDP Learning
When the pulse value that the injector starts injection is measured, it is called minimum drive pulse
(MDP). Through MDP controls, can correct pilot injections effectively. Pilot injection volume is very
small, 1 to 2 mm/str, so precise control of the injector can be difficult if it gets old. So there needs MDP
learning to control the very small volume precisely through learning according to getting older injectors.
Control the fuel injection volume precisely by MDP learning even for the old injector.
ECU corrects the pilot injection effectively by MDP control.
MDP learning is performed by the signal from knock sensor. -
-
- The system measures the pulse at initial injection to reduce the engine vibration.
B. Purpose of MDP learning
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(7) Knocking Control
A. Resetting the pilot injection
The knocking control is used to reset the pilot injection flow in closed loop for each injector. This
method allows the correction of any injector deviations over a period of time. The principle of use of the
knocking control is based on the detection of the combustion noises.
The sensor is positioned in such a way as to receive the maximum signal for all the cylinders. The raw
signals from the knock sensor are processed to obtain a variable which quantifies the intensity of the
combustion. This variable, known as the ratio, consists of the ratio between the intensity of the
background noise and the combustion noise.
A first window is used to establish the background noise level of the knocking control signal for
each cylinder. This window must therefore be positioned at a moment when there cannot be any
combustion.
The second window is used to measure the intensity of the pilot combustion. Its position is such
that only the combustion noises produced by the pilot injection are measured . It is therefore
placed just before the main injection. 1.
2.
The knock sensor does not allow any evaluation of the quantity injected. However, the pulse value will
be measured when the injector starts injection and this pulse value is called the MDP (Minimum Drive
Pulse). On the basis of this information, it is possible to efficiently correct the pilot flows. The pilot
injection resetting principle therefore consists of determining the MDP, in other words the pulse
corresponding to the start of the increase in value of the ratio (increase of vibration due to fuel
combustion).