The Multiport Fuel Injection System consists of
sensors which detect the engine conditions, the
POWERTRAIN CONTROL MODULE (PCM) which
controls the system based on signals from these
sensors, and actuators which operate 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 is
equipped with several diagnostic test modes which
simplify troubleshooting when a problem develops.

FUEL INJECTION CONTROL
The injector drive times and injector timing are
controlled so that the optimum air/fuel mixture is
supplied 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
regulator. 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 1-2-3-4-5-6. 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 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 PCM 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 obtains the
maximum cleaning performance.

IDLE AIR CONTROL
The idle speed is kept at the optimum speed by
controlling the amount of air that bypasses the
throttle valve in accordance with changes in idling
conditions and engine load during idling. The PCM
drives the idle air control (IAC) motor to keep the
engine running at the pre-set idle target speed in
accordance with the engine coolant temperature 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 IAC motor adjusts the throttle
valve bypass 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
primary 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
PCM from engine speed, intake air volume, engine
coolant temperature, and atmospheric pressure.

DIAGNOSTIC TEST MODE

•

When an abnormality is detected in one of the
sensors or actuators related to emission control,
the SERVICE ENGINE SOON/MALFUNCTION
INDICATOR LAMP illuminates to warn the driver.

•

When an abnormality is detected in one of the
sensors or actuators, a diagnostic trouble code
corresponding to the abnormality 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 scan tool MUT-II (MB991502) under
certain circumstances.

OTHER CONTROL FUNCTIONS

1. 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.

2. A/C Compressor Clutch Relay Control Turns the

compressor clutch of the A/C ON and OFF.

3. Fan Relay Control The radiator fan and

condenser fan speeds are controlled in response
to the engine coolant temperature and vehicle
speed.

4. Generator Output Current Control Prevents

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

5. Evaporative Emission Purge Control (Refer to

GROUP 17, Emission Control System

−

Evaporative Emission Control System

−

General

Information.

P.17-83

)

6. EGR Control (Refer to GROUP 17, Emission

Control System

−

Exhaust Gas Recirculation

(EGR) System

−

General Information.

P.17-88

)

GENERAL INFORMATION

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-3

MULTIPORT FUEL INJECTION (MFI) SYSTEM DIAGRAM

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

P.17-77

AK000045

CATALYTIC CONVERTER

FUEL PRESSURE
REGULATOR

M*1

EGR
VALVE

DASH
POT
<M/T>

FROM

FUEL

PUMP

FUEL

TANK

1 LEFT BANK 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 LEFT BANK HEATED OXYGEN SENSOR (REAR)
10 RIGHT BANK HEATED OXYGEN SENSOR (FRONT)
11 RIGHT BANK HEATED OXYGEN SENSOR (REAR)
12 MANIFOLD DIFFERENTIAL PRESSURE SENSOR
13 FUEL TANK DIFFERENTIAL PRESSURE SENSOR

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

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

PCM

SENSE

DECIDE

ACT

NOTE

*1 : Manifold port
*2 : Restrictor

3 INTAKE AIR
TEMPERATURE SENSOR

2, 7

VOLUME AIR FLOW SENSOR
(WITH BAROMETRIC
PRESSURE SENSOR)

3 IDLE AIR
CONTROL
MOTOR

4 THROTTLE POSITION SENSOR

12 MANIFOLD DIFFERENTIAL
PRESSURE SENSOR

1 INJECTOR

CHAMBER

VCV

EGR
5 SOLENOID

EVAPORATIVE EMISSION

2 PURGE SOLENOID

8 ENGINE

COOLANT

TEMPERATURE

SENSOR

10 RIGHT BANK

HEATED OXYGEN

SENSOR (FRONT)

11 RIGHT BANK

HEATED OXYGEN

SENSOR (REAR)

CRANKSHAFT POSITION

SENSOR

9 LEFT BANK HEATED
OXYGEN SENSOR (REAR)

5 CAMSHAFT
POSITION
SENSOR

13 FUEL TANK
DIFFERENTIAL
PRESSURE SENSOR

LEFT BANK
HEATED
1 OXYGEN
SENSOR
(FRONT)

EVAPORATIVE
EMISSION
CANISTER

4 EVAPORATIVE
EMISSION

VENTILATION

SOLENOID

FUEL TANK

AIR INLET

DISTRIBUTOR

IGNITION
COIL

VENT VALVE

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-4

M U LTIPO R T FU EL IN JEC TIO N (M FI) D IA G N O SIS

TROUBLESHOOTING STRATEGY

M1131008500101

NOTE: If a DTC is erased, its "freeze frame" data will
be also erased and the readiness test status will be
reset. Store the "freeze frame" data before erasing
the DTC.
Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will be sure to have
exhausted most of the possible ways to find an MFI
fault.
1. Gather as much information as possible about the

complaint from the customer.

2. Verify that the condition described by the

customer exists.

3. Check the vehicle for any MFI Diagnostic Trouble

Code (DTC).

4. If you cannot verify the condition and there are no

DTCs, the malfunction is intermittent. For
information on how to cope with intermittent
malfunctions, refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points

−

How

to cope with Intermittent Malfunction

P.00-8

5. If you can verify the condition but there are no

DTCs, or the system cannot communicate with
the scan tool, refer to the trouble symptom
classification table.

6. If there is a DTC, record the number of the code,

then erase the code from the memory using the
scan tool.

7. Reconfirm the malfunction symptom and carry out

a test drive with the drive cycle pattern.

8. If DTC is set again, carry out an inspection with

the inspection procedure for diagnostic trouble
codes of that code.

9. If DTC is not set again, the malfunction is

intermittent. For information on how to cope with
intermittent malfunctions, refer to GROUP 00,
How to Use Troubleshooting/Inspection Service
Points

−

How to cope with Intermittent Malfunction

P.00-8

10.After repairs are completed, conduct a road test

duplicating the complaint set conditions to confirm
the malfunction has been connected.

NOTE: If the powertrain control module (PCM) is
replaced, the immobilizer-ECU should be replaced
together with it. Each PCM has an individual
information for immobilizer-ECU, and the individual
information is registered in the immobilizer-ECU.

TROUBLE CODE DIAGNOSIS

M1131008600108

SERVICE ENGINE SOON/MALFUNCTION INDICATOR
LAMP
Among the on-board diagnostic items, a Service Engine Soon/
Malfunction Indicator Lamp illuminates to notify the driver of an
emission control malfunction.
However, when an irregular signal returns to normal and the
powertrain control module judges that it has returned to normal,
the Service Engine Soon/Malfunction Indicator Lamp is
switched off.
Moreover, when the ignition switch is turned off, the lamp is
switched off. Even if the ignition switch is turned on again, the
lamp does not illuminate until the malfunction is detected.
Immediately after the ignition switch is turned on, the Service
Engine Soon/Malfunction Indicator Lamp is lit for five seconds
to indicate that the Service Engine Soon/Malfunction Indicator
Lamp operates normally.

AK000605AB

SERVICE ENGINE SOON/
MALFUNCTIONINDICATOR LAMP

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