The Multiport Fuel Injection System consists of sen-
sors, actuators and the engine control module (ECM)
<M/T> or powertrain control module (PCM) <A/T>.
The sensors detect the engine condition. The mod-
ule controls the system based on signals from these
sensors. The actuators work under the control of the
ECM <M/T> or PCM <A/T>. The ECM <M/T> or
PCM <A/T> carries out activities such as fuel injec-
tion control, idle air control, and ignition timing con-
trol. In addition, the ECM <M/T> or PCM <A/T> is
equipped with several diagnostic test modes which
simplify troubleshooting when a problem develops.

FUEL INJECTION CONTROL
The ECM <M/T> or PCM <A/T> controls injector
drive times and injection timing to supply the opti-
mum air/fuel mixture to the engine according to the
continually-changing engine operation conditions. A
single injector is mounted at the intake port of each
cylinder. The fuel pump supplies pressurized fuel
from the fuel tank to the fuel injectors. The fuel pres-
sure regulator controls the fuel pressure. Thus, the
regulated fuel is distributed to each injector. Fuel is
normally injected for each cylinder every two rota-
tions of the crankshaft. The firing order is 1-3-4-2.
Each cylinder has a dedicated fuel injector. This is
called "multiport." The ECM <M/T> or PCM <A/T>
provides a richer air/fuel mixture by carrying out
"open-loop" control when the engine is cold or run-
ning under high load conditions. Thus, engine perfor-
mance is maintained. In addition, when the engine is
under normal operating temperature after warm-
ing-up, the ECM <M/T> or PCM <A/T> controls the
air/fuel mixture according to the heated oxygen sen-
sor signal. This control is a "closed-loop" control. The
closed-loop control achieves the theoretical air/fuel
mixture ratio where the catalytic converter can obtain
the maximum cleaning performance.

IDLE AIR CONTROL
The engine control module controls the amount of air
that bypasses the throttle valve according to
changes in idling conditions and engine load during
idling. Thus, idle speed is kept at an optimum speed.
The ECM <M/T> or PCM <A/T> drives the idle air
control (IAC) motor according to engine coolant tem-
perature, A/C, and other electrical load. Thus, idle
speed is kept at an optimum speed. In addition,

when the A/C switch is turned off and on while the
engine is idling, the IAC motor adjusts the throttle
valve bypass air amount. Thus, idle speed is main-
tained at constant speed regardless of various
engine load conditions.

IGNITION TIMING CONTROL
The ignition power transistor located in the ignition
primary circuit turns on and off to control primary cur-
rent flow to the ignition coil. This maintains ignition
timing at an optimum level regardless of various
engine operating conditions. The ECM <M/T> or
PCM <A/T> determines the ignition timing according
to engine speed, intake air volume, engine coolant
temperature, and atmospheric pressure.

DIAGNOSTIC TEST MODE

• When a fault is detected in any 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 <M/T> or
PCM <A/T>.

• The RAM data inside the ECM <M/T> or PCM

<A/T> that is related to the sensors and actuators
can be read with the scan tool. In addition, the
actuators can be controlled by the scan tool
MB991958 (MUT-III Sub Assembly) under certain
circumstances.

OTHER CONTROL FUNCTIONS

• Fuel Pump Control

Turns on the fuel pump relay so that current is
supplied to the fuel pump while the engine is
cranking or running.

• A/C Compressor Clutch Relay Control

Turns on and off the air conditioning compressor
clutch.

• Evaporative Emission Purge Control

(Refer to GROUP 17, Emission Control System

−

Evaporative Emission System

− General Informa-

tion

P.17-103

• EGR Control

(Refer to GROUP 17, Emission Control System

−

Exhaust Gas Recirculation (EGR) System

− Gen-

eral Information

P.17-109

GENERAL DESCRIPTION

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-4

MULTIPORT FUEL INJECTION (MFI) SYSTEM DIAGRAM

NOTE: For the vacuum hose routing, refer to
GROUP 17, Vacuum Hoses

P.17-95

AK300836

AK300836AB

AIR INLET

3 INTAKE AIR
TEMPERATURE SENSOR

3 IDLE AIR
CONTROL
MOTOR

VOLUME AIR FLOW SENSOR
(WITH BAROMETRIC
PRESSURE SENSOR)

12 FUEL TANK DIFFERENTIAL
PRESSURE SENSOR

EVAPORATIVE
EMISSION CANISTER

FUEL TANK

5 EVAPORATIVE
EMISSION
VENTILATION
SOLENOID

2 EVAPORATIVE
EMISSION
PURGE
SOLENOID

4 EGR VACUUM
REGULATOR
SOLENOID VALVE

4 THROTTLE
POSITION
SENSOR

MANIFOLD
ABSOLUTE
PRESSURE
SENSOR
11

EGR VALVE

VACUUM
CONTROL
VALVE

M*1

FROM
FUEL
PUMP

TO FUEL
TANK

FUEL
PRESSURE
REGULATOR

5 CAMSHAFT
POSITION
SENSOR

8 ENGINE COOLANT
TEMPERATURE
SENSOR

1 HEATED OXYGEN SENSOR (FRONT)

9 KNOCK SENSOR

6 CRANKSHAFT
POSITION SENSOR

10 HEATED OXYGEN SENSOR (REAR)

NOTE
*1 : Manifold port
*2 : Restrictor

13 FUEL TEMPERATURE
SENSOR

14 FUEL LEVEL SENSOR

1 INJECTOR

1 HEATED OXYGEN SENSOR (FRONT)
2 VOLUME AIR FLOW SENSOR
3 INTAKE AIR TEMPERATURE SENSOR
4 THROTTLE POSITION SENSOR
5 CAMSHAFT POSITION SENSOR
6 CRANKSHAFT POSITION SENSOR
7 BAROMETRIC PRESSURE SENSOR
8 ENGINE COOLANT TEMPERATURE SENSOR
9 KNOCK SENSOR
10 HEATED OXYGEN SENSOR (REAR)
11 MANIFOLD ABSOLUTE PRESSURE SENSOR
12 FUEL TANK DIFFERENTIAL PRESSURE SENSOR
13 FUEL TEMPERATURE SENSOR
14 FUEL LEVEL SENSOR

POWER SUPPLY
A/C PRESSURE SENSOR
VEHICLE SPEED SENSOR <M/T>
OUTPUT SHAFT SPEED SENSOR <A/T>
A/C SWITCH
TRANSMISSION RANGE SWITCH <A/T>
POWER STEERING PRESSURE SWITCH
IGNITION SWITCH - ST

1 INJECTOR
2 EVAPORATIVE EMISSION
PURGE SOLENOID
3 IDLE AIR CONTROL MOTOR
4 EGR VACUUM REGULATOR
SOLENOID VALVE
5 EVAPORATIVE EMISSION
VENTILATION SOLENOID

FUEL PUMP RELAY 1, 2
MULTIPORT FUEL INJECTION
(MFI) RELAY
A/C COMPRESSER CLUTCH RELAY
MALFUNCTION INDICATOR LAMP
(SERVICE ENGINE SOON OR
CHECK ENGINE LAMP)
DIAGNOSTIC OUTPUT
IGNITION COIL,
IGNITION POWER TRANSISTER

ECM <M/T>
PCM <A/T>

SENSE

DECIDE

ACT

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