Mitsubishi Montero Sport (2004+). Manual - part 364

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-869

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Required Special Tools:

• MB991709: Test Harness Set

.

Measurement Method
1. Disconnect the idle air control motor connector, and connect 

the test harness special tool (MB991709) in between. (All 
terminals should be connected.) 

2. Connect the oscilloscope probe to the idle air control motor 

connector terminal No. 1, terminal No. 3, terminal No. 4 and 
terminal No. 6 respectively.

.

Alternate method (Test harness not available)
1. Connect the oscilloscope probe to PCM terminals No. 14, 

No. 15, No. 28 and No. 29.

Standard Wave Pattern

Observation conditions

Function

Special pattern

Pattern height

High

Pattern selector

Display

Engine condition

Turn the ignition switch from 
"OFF" to "ON" (without 
starting the engine).

While the engine is idling, 
turn the A/C switch to ON.

Immediately after starting the 
warm the engine 
(approximately one minute).

AK102983AB

1 2 3
4 5 6

IDLE AIR CONTROL
MOTOR CONNECTOR

OSCILLOSCOPE

MB991709

AKX01607 AB

(V)

30

20

10

0

IAC
MOTOR
CONTROL
SIGNAL
WAVE
PATTERN

THE WAVE PATTERN
APPEARS FOR AN
INSTANT, BUT SOON
DISAPPEARS.

POINT B COIL RE-
VERSE ELECTRO-
MOTIVE FORCE
(APPROXIMATELY
3 x10 V)

POINT AN INDUCED
ELECTROMOTIVE
FORCE FROM THE
MOTOR TURNING

TIME

Standard wave pattern

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-870

Wave Pattern Observation Points

1. Check that the standard wave pattern appears when the 

idle air control motor is operating.

Point A:Presence or absence of induced electromotive force 

from the motor turning. (Refer to abnormal wave pattern.)

Point B:Height of coil back electromotive force

.

Examples of Abnormal Wave Patterns
Example 1
Cause of problem

• Malfunction of motor. (Motor is not operating.)

Wave pattern characteristics

• Induced electromotive force from the motor turning does 

not appear.

Example 2
Cause of problem

• Open circuit in the line between the idle air control motor 

and the PCM.

Wave pattern characteristics

• Current is not supplied to the motor coil on the open cir-

cuit side. (Voltage does not drop to 0 volt.) Furthermore, 
the induced electromotive force wave pattern at the nor-
mal side is slightly different from the normal wave pat-
tern.

CONTRAST WITH 
STANDARD WAVE 
PATTERN

PROBABLE CAUSE

Induced electromotive force 
does not appear or is 
extremely small

Malfunction of motor

CONTRAST WITH 
STANDARD WAVE 
PATTERN

PROBABLE CAUSE

Coil reverse electromotive 
force does not appear or is 
extremely small

Short in the coil

AKX01608 AB

AKX01609

OPEN
CIRCUIT
SIDE

NORMAL
SIDE

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-871

IGNITION COIL AND IGNITION POWER 
TRANSISTOR

Required Special Tool:

• MB991348: Test Harness Set

.

Measurement Method
1. Disconnect the connector, and connect test harness special 

tool (MB991348) in between. (All terminals should be 
connected.)

2. Connect the oscilloscope probe to each ignition power 

transistor connector terminal to analyze each cylinder:

• Terminal No. 1 for the number 3 and 6 cylinders

• Terminal No. 2 for the number 2 and 5 cylinders

• Terminal No. 3 for the number 1 and 4 cylinders

.

Alternate method (Test harness not available)
1. Connect the oscilloscope probe to PCM terminal No. 11. 

(When checking the number 1 and 4 cylinders.)

2. Connect the oscilloscope probe to PCM terminal No. 12. 

(When checking the number 3 and 6 cylinders.)

3. Connect the oscilloscope probe to PCM terminal No. 13. 

(When checking the number 2 and 5 cylinders.)

Standard Wave Pattern

Observation conditions

Function

Special pattern

Pattern height

Variable

Pattern selector

Display

Engine r/min

Approximately 1,200 r/min

AK102986

1 2 3 4 5 6

OSCILLOSCOPE

IGNITION POWER
TRANSISTOR

MB991348

AB

AK000726

0

2

4

6

0

2

4

6

T

T : CRANKSHAFT ANGLE (120

)

COMPRESSION
TOP DEAD CENTER

POINT : WAVE
              BUILD-UP
              SECTION

˘

˘

:SPARK

     ADVANCE
     ANGLE

ON

DWELL SECTION

OFF

TIME

(V)

IGNITION POWER
TRANSISTOR
CONTROL SIGNAL
WAVE PATTERN

CRANKSHAFT
POSITION
SENSOR OUTPUT
WAVE PATTERN
(REFERENCE)

Standard wave pattern

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-872

Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum 

voltage (Refer to abnormal wave pattern examples 1 and 
2.)

.

Examples of Abnormal Wave Patterns
Example 1 (Wave pattern during engine cranking)
Cause of problem

• Open-circuit in ignition primary circuit

Wave pattern characteristics

• Top-right part of the build-up section cannot be seen, 

and voltage value is approximately 2 volts too low.

Example 2 (Wave pattern during engine cranking)
Cause of problem

• Malfunction in ignition power transister

Wave pattern characteristics

• Power voltage results when the ignition power transistor 

is ON.

CONDITION OF WAVE 
PATTERN BUILD-UP 
SECTION AND MAXIMUM 
VOLTAGE

PROBABLE CAUSE

Rises from approximate 2 
volts to approximate 4.5 volts 
at the top-right

Normal

2-volt rectangular wave

Open-circuit in ignition primary 
circuit

Rectangular wave at power 
voltage

Ignition power transistor 
malfunction

AKX01612

NORMAL WAVE
PATTERN

2V

AB

AKX01613

BATTERY
POSITION
VOLTAGE

NORMAL WAVE
PATTERN

AB