The Multiport Fuel Injection System consists of sen-
sors which detect the engine conditions, the ENGINE
CONTROL MODULE (ECM) which controls the sys-
tem based on signals from these sensors, and actua-
tors which operate under the control of the ECM.
The ECM carries out activities such as fuel injection
control, idle air control, and ignition timing control.
In addition, the ECM is equipped with several diag-
nostic test modes which simplify troubleshooting
when a problem develops.

FUEL INJECTION CONTROL

The injector drive times and injection timing are con-
trolled so that the optimum air/fuel mixture is sup-
plied to the engine to correspond to the
continually-changing engine operation conditions.
A single injector is mounted at the intake port of each
cylinder. Fuel is sent under pressure from the fuel
tank to the fuel injectors by the fuel pump, with the
pressure being regulated by the fuel pressure regula-
tor. The regulated fuel is distributed to each of the
injectors.
Fuel injection is normally carried out once for each
cylinder for every two rotations of the crankshaft.
The firing order is 1-3-4-2. Each cylinder has a dedi-
cated fuel injector. This is called multiport.
The ECM provides a richer air/fuel mixture by carry-
ing out "open-loop" control when the engine is cold
or operating under high load conditions in order to
maintain engine performance.In addition, when the
engine is under normal operating temperature after
warming-up, the ECM controls the air/fuel mixture by
using the heated oxygen sensor signal to carry out
"closed-loop" control. The closed-loop control
achieves the theoretical air/fuel mixture ratio where
the catalytic converter can obtain the maximum
cleaning performance.

THROTTLE VALVE OPENING CONTROL

This system electrically controls the opening of the
throttle valve. The ECM detects the amount of travel
of the accelerator pedal via the accelerator pedal
position sensor, and controls the actuation of the
throttle actuator control motor, which is mounted on
the throttle body, in order to attain the target throttle
valve opening that has been predetermined in accor-
dance with driving conditions.

IDLE AIR CONTROL

The idle speed is kept at the optimum speed by con-
trolling the amount of air that passes through the
throttle valve in accordance with changes in idling
conditions and engine load during idling.
The ECM drives the throttle actuator control motor to
keep the engine running at the pre-set idle target
speed in accordance with the engine coolant temper-
ature and A/C and other electrical load. In addition,
when the air conditioning switch is turned off and on
while the engine is idling, the throttle actuator control
motor adjusts the throttle valve pass-through air
amount according to the engine load conditions to
avoid fluctuations in the engine speed.

IGNITION TIMING CONTROL

The ignition power transistor located in the ignition
primary circuit turns ON and OFF to control the pri-
mary current flow to the ignition coil. This controls the
ignition timing to provide the optimum ignition timing
with respect to the engine operating conditions. The
ignition timing is determined by the ECM from engine
speed, intake air volume, engine coolant tempera-
ture, and atmospheric pressure.

DIAGNOSTIC TEST MODE

• When a fault is detected in one of the sensors or

actuators related to emission control, the Mal-
function Indicator Lamp (SERVICE ENGINE
SOON or Check Engine Lamp) illuminates to
warn the driver.

• When a fault is detected in one of the sensors or

actuators, a diagnostic trouble code correspond-
ing to the fault is stored in the ECM.

• The RAM data inside the ECM that is related to

the sensors and actuators can be read with the
scan tool. In addition, the actuators can be con-
trolled by scan tool MB991958 (M.U.T.-III sub
assembly) under certain circumstances.

GENERAL INFORMATION

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MULTIPORT FUEL INJECTION (MFI)

13A-3

OTHER CONTROL FUNCTIONS

Fuel Pump Control

• Turns the fuel pump relay ON so that current is

supplied to the fuel pump while the engine is
cranking or running.

• In accordance with the driving conditions,

switches the actuation condition of the fuel pump.

A/C Compressor Clutch Relay Control

• Turns the compressor clutch of the A/C ON and

OFF.

Engine Oil Control Valve Control

• The ECM carries out the duty control of the

engine oil control valve according to the opera-
tion condition. This varies the phase angle of the
camshaft to optimize the valve timing.

Intake Charge Pressure Control

• Control the intake charge pressure by controlling

the duty of the turbocharger wastegate solenoid.

Generator Output Current Control

• Prevent generator output current from increasing

suddenly and idle speed from dropping at times
such as when the headlights are turned on.

Evaporative Emission Purge Control

• (Refer to GROUP 17, Emission Control − Evapo-

rative Emission Control System

− General Infor-

mation

P.17-74

GENERAL INFORMATION

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-4

MULTIPORT FUEL INJECTION (MFI) SYSTEM DIAGRAM

NOTE: For the vacuum routing, refer to GROUP 17, Emission Control

−

Vacuum Hoses

−

Vacuum Hose Rout-

ing

P.17-70

AK703839

1 Mass airflow sensor
2 Intake air temperature sensor 1
3 Throttle position sensor (main)
4 Throttle position sensor (sub)
5 Manifold absolute pressure sensor
6 Intake air temperature sensor 2
7 Engine coolant temperature sensor
8 Intake camshaft position sensor
9 Exhaust camshaft position sensor
10 Crankshaft position sensor
11 Knock sensor
12 Heated oxygen sensor (front)
13 Heated oxygen sensor (rear)
14 Fuel tank differential pressure sensor
15 Fuel tank temperature sensor

Ignition switch-IG
Ignition switch-ST
Power supply
CAN communication (input signal)

1 Intake engine oil control valve
2 Exhaust engine oil control valve
3 Throttle actuator control motor
4 Injector
5 Evaporative emission purge solenoid

7 Turbocharger wastegate solenoid 1
8 Turbocharger wastegate solenoid 2

6 Evaporative emission ventilation
solenoid

Ignition coil, ignition power transistor
Multiport fuel injection (MFI) relay
Fuel pump relay 1
Fuel pump relay 2
Starter relay
Throttle actuator control motor relay
Generator G terminal
Heated oxygen sensor heater
A/C compressor relay
CAN communication (output signal)

Sense

Act

Engine oil pressure switch
Power steering pressure switch
Generator FR terminal
Generator L terminal
Clutch pedal position switch <M/T>

Accelerator pedal position sensor (main)
Accelerator pedal position sensor (sub)

Decide

ECM
(with barometric
pressure sensor)

Fuel level
sensor

To fuel
tank

Fuel
pressure
regulator

Air
inlet

2
Exhaust engine
oil control valve

1 Intake engine
oil control valve

5 Manifold
absolute
pressure
sensor

6 Intake air
temperrature
sensor 2

2 Intake air
temperature
sensor 1

1 Mass airflow sensor

8
Intake camshaft
position sensor

9 Exhaust camshaft position sensor

3 Throttle position sensor (main)

4 Throttle position sensor (sub)

5 Evaporative emission
purge solenoid

3 Throttle actuator control motor

15 Fuel tank
temperature
sensor

14 Fuel tank
differential
puressure
sensor

13 Heated oxygen sensor (rear)

12 Heated oxygen sensor (front)

10 Crankshaft position sensor

7 Engine coolant
temperature sensor

11 Knock sensor

4 Injector

Fuel pump

Fuel tank

Evaporative
emission
canister

6 Evaporative
emission
ventilation
solenoid

Check valve

Bypass valve

Turbocharger
wastegate actuator

7 Turbocharger
wastegate solenoid 1

8 Turbocharger
wastegate solenoid 2

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