SsangYong Rexton. Service manual - part 89

DI08-9

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EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

ECU Inputs·Outputs

Control

E

C

U

Structure and Function of ECU

Function of ECU

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 ~ +85°C and protected from factors like oil, water and electromag-
netism 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.

Output

Injector

EGR system

Fuel pressure regulating valve (IMV)

Electrical fan control (Low/High-speed)

A/C compressor relay

Glow plug relay

Immobilizer

Warning lights

(Water warning light, glow plug indica-

tor light, engine warning light)

Preheater (auxiliary heater)

K - line

CAN communication

Self-diagnosis

Inputs

Booster pressure sensor

Atmospheric pressure sensor
(Built-in ECU)

Air flow sensor (HFM)

Coolant temperature sensor

Fuel temperature sensor

Fuel pressure sensor

Fuel filter water sensor

Knock sensor

crankshaft position sensor

camshaft position sensor

Accelerator sensor

Vehicle speed sensor

Switch input signal

(IG, brake, clutch, A/C signal, A/C

compressor)

DI08-10

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ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

Control Function of ECU

• 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.

DI08-11

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ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

ECU - Removal and Installation

1. Flip up the front passenger’s seat and remove the ECU

cover nuts.

2. Remove the ECU bracket nuts.

Y220_08005

Y220_08006

Y220_08007

3. Unscrew the ECU connect bolt and remove the ECU

assembly.

4. Install in the reverse order of removal.

5. Backup the below data with Scan-i when replacing the

ECU.

- Current ECU data

- Vehicle Identification Number (VIN)

- Variant coding data

- Then, input the data into new ECU. For immobilizer

equipped vehicle, additional coding operation is
necessary.

DI08-12

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EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

FUEL PRESSURE CONTROL

Fuel Pressure Control Elements

Pressure control consists of 2 principle modules.

• Determines rail pressure according to engine operating conditions.

• Controls IMV to make the rail pressure to reach to the required value.

Pressure in the fuel rail is determined according to engine speed and load on the engine. The aim is to adapt the
injection pressure to the engine’s requirements.

• When engine speed and load are high

: The degree of turbulence is very great and the fuel can be injected at very high pressure in order to optimize

combustion.

• When engine speed and load are low

: The degree of turbulence is low. If injection pressure is too high, the nozzle’s penetration will be excessive and part

of the fuel will be sprayed directly onto the sides of the cylinder, causing incomplete combustion. So there occurs
smoke and damages engine durability.

Fuel pressure is corrected according to air temperature, coolant temperature and atmospheric pressure and to take
account of the added ignition time caused by cold running or by high altitude driving. A special pressure demand is
necessary in order to obtain the additional flow required during starts. This demand is determined according to injected
fuel and coolant temperature.

Fuel Pressure Control

Rail pressure is controlled by closed loop regulation of IMV. A mapping system – open loop – determines the current
which needs to be sent to the actuator in order to obtain the flow demanded by the ECU. The closed loop will correct the
current value depending on the difference between the pressure demand and the pressure measured.

• If the pressure is lower than the demand, current is reduced so that the fuel sent to the high pressure pump is

increased.

• If the pressure is higher than the demand, current is increased so that the fuel sent to the high pressure pump is

reduced.

Y220_08008

Flow demand

Engine speed

Measured rail

pressure

Open

IMV current

IMV

Current

PIG

governor

Error

Correction

Rail pressure

demand