The Multiport Fuel Injection System consists of
sensors, actuators and the powertrain control
module (PCM). The sensors detect the engine
condition. The module controls the system based on
signals from these sensors. The actuators work
under the control of the PCM. The PCM carries out
activities such as fuel injection control, idle air
control, and ignition timing control. In addition, the
PCM has several diagnostic test modes which
simplify troubleshooting when a problem develops. In
addition, the PCM is equipped with several
diagnostic test modes which simplify troubleshooting
when a problem develops.

FUEL INJECTION CONTROL
The PCM controls injector drive times and injector
timing to supply the optimum 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 pressure regulator controls
the fuel pressure. Thus, the regulated fuel is
distributed to each injector. Fuel is normally injected
for each cylinder every two rotations of the
crankshaft. The firing order is 1-3-4-2. Each cylinder
has a dedicated fuel injector. This is called
"multiport." The PCM provides a richer air/fuel
mixture by carrying out "open-loop" control when the
engine is cold or running under high load conditions.
Thus, engine performance is maintained. In addition,
when the engine is under normal operating
temperature after warming-up, the PCM controls the
air/fuel mixture according to the heated oxygen
sensor 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 PCM drives the idle air control (IAC) motor
according to engine coolant temperature, A/C, and

other electrical load. Thus, idle speed is kept at an
optimum speed. In addition, when the air
conditioning 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
maintained 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
current flow to the ignition coil. This maintains
ignition timing at an optimum level regardless of
various engine operating conditions. The PCM
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
SERVICE ENGINE SOON/MALFUNCTION
INDICATOR LAMP illuminates to warn the driver.

•

When a fault is detected in one of the sensors or
actuators, a diagnostic trouble code
corresponding to the fault is stored in the PCM.

•

The RAM data inside the PCM 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 MUT-II (MB991502)
under certain circumstances.

OTHER CONTROL FUNCTIONS

1. 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.

2. A/C Compressor Clutch Relay Control Turns on

and off the air conditioning compressor clutch.

3. Evaporative Emission Purge Control (Refer to

GROUP 17, Emission Control System

−

Evaporative Emission Control System

−

General

Information.

P.17-83

)

4. EGR Control (Refer to GROUP 17, Emission

Control System

−

Exhaust Gas Recirculation

(EGR) System

−

General Information.

P.17-88

)

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.17-77

AK000583

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 HEATED OXYGEN SENSOR (REAR)
10 MANIFOLD DIFFERENTIAL PRESSURE SENSOR
11 FUEL TANK DIFFERENTIAL PRESSURE SENSOR

POWER SUPPLY
VEHICLE SPEED SENSOR
A/C SWITCH
PARK/NEUTRAL POSITION SWITCH
POWER STEERING PRESSURE SWITCH
IGNITION SWITCH - ST

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

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

PCM

SENSE

DECIDE

ACT

AIR INLET

3 INTAKE AIR
TEMPERATURE SENSOR

3 IDLE AIR
CONTROL
MOTOR

7, 2

VOLUME AIR FLOW SENSOR
(WITH BAROMETRIC
PRESSURE SENSOR)

11 FUEL TANK
DIFFERENTIAL
PRESSURE
SENSOR

EVAPORATIVE
EMISSION
CANISTER

FUEL TANK

5 EVAPORATIVE
EMISSION
VENTILATION
SOLENOID

2 EVAPORATIVE

EMISSION

PURGE

SOLENOID

4 EGR
SOLENOID

4 THROTTLE POSITION
SENSOR

MANIFOLD
DIFFERENTIAL
PRESSURE
SENSOR
10

EGR
VALVE

VACUUM

CONTROL

VALVE

M*1

FROM

FUEL

PUMP

FUEL

TANK

FUEL

PRESSURE

REGULATOR

INJE-
CTOR

5 CAMSHAFT
POSITION
SENSOR

ENGINE COOLANT

TEMPERATURE

SENSOR

1 HEATED OXYGEN SENSOR (FRONT)

6 CRANK SHAFT
POSITION SENSOR

9 HEATED OXYGEN SENSOR (REAR)

NOTE

*1 : Manifold port
*2 : Restrictor

Content .. 78 79 80 81 ..