Mitsubishi Pajero Pinin. Manual — part 126
MPI <4G9> –
Troubleshooting
13C-90
Examples of Abnormal Wave Patterns
D
Example 1
Cause of problem
Sensor interface malfunction
Wave pattern characteristics
Rectangular wave pattern is output even when the engine
is not started.
D
Example 2
Cause of problem
Loose timing belt
Abnormality in sensor disk
Wave pattern characteristics
Wave pattern is displaced to the left or right.
INJECTOR
Measurement Method
1.
Disconnect the injector connector, and then connect the
special tool (test harness: MB991348) in between.
(Both the power supply side and engine-ECU side should
be connected.)
2.
Connect the analyzer special patterns pickup to terminal
2 of the injector connector.
Alternate Method (Test harness not available)
1.
Connect the analyzer special patterns pickup to
engine-ECU terminal 1. (When checking the No. 1
cylinder.)
2.
Connect the analyzer special patterns pickup to
engine-ECU terminal 14. (When checking the No. 2
cylinder.)
3.
Connect the analyzer special patterns pickup to
engine-ECU terminal 2. (When checking the No. 3
cylinder.)
4.
Connect the analyzer special patterns pickup to
engine-ECU terminal 15. (When checking the No. 4
cylinder.)
Analyzer
MPI <4G9> –
Troubleshooting
13C-91
Standard Wave Pattern
Observation conditions
Function
Special patterns
Pattern height
Variable
Variable knob
Adjust while viewing the wave pattern
Pattern selector
Display
Engine r/min
Idle speed
Standard wave pattern
(V)
Point A
Point B
Solenoid back electromotive force
(Approx. 7
×
10 V)
Injector drive time
Power voltage
Drive signal: ON
Drive signal: OFF
Time
50
0
Wave Pattern Observation Points
Point A: Height of solenoid back electromotive force
Contrast with standard wave pattern
Probable cause
Solenoid coil back electromotive force is low or doesn’t
appear at all.
Short in the injector solenoid
Point B: Injector drive time
D
The injector drive time will be synchronized with the MUT-
II
tester display.
D
When the engine is suddenly raced, the drive time will
be greatly extended at first, but the drive time will soon
match the engine speed.
When idling
When racing
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MPI <4G9> –
Troubleshooting
13C-92
IDLE SPEED CONTROL (ISC) SERVO (STEPPER
MOTOR)
Measurement Method
1.
Disconnect the ISC servo connector, and connect the
special tool (test harness: MB991709) in between.
2.
Connect the analyzer special patterns pickup to the ISC
servo-side connector terminal 1, terminal 3, terminal 4
and terminal 6 respectively.
Alternate Method (Test harness not available)
1.
Connect the analyzer special patterns pickup to
engine-ECU terminal 4, connection terminal 5, connection
terminal 17, and connection terminal 18 respectively.
Standard Wave Pattern
Observation conditions
Function
Special patterns
Pattern height
High
Pattern selector
Display
Engine condition
When the engine coolant temperature is 20
_
C or below, turn the ignition switch from LOCK
(OFF) position to ON (without starting the engine).
While the engine is idling, turn the A/C switch to ON.
Immediately after starting the warm engine
Standard wave pattern
Stepper
motor
control
signal
wave
pattern
(V)
30
20
10
The wave pattern
appears for an
instant, but soon
disappears.
Point B
Coil reverse electromotive
force (Approx. 3
×
10V)
Point A
Induced electromotive force
from the motor turning
Time
Special
patterns
pickup
Analyzer
MPI <4G9> –
Troubleshooting
13C-93
Wave Pattern Observation Points
Check that the standard wave pattern appears when the stepper motor is operating.
Point A:
Presence or absence of induced electromotive force from the motor turning. (Refer to the abnormal
wave pattern.)
Contrast with standard wave pattern
Probable cause
Induced electromotive force does not appear or is extremely small.
Motor is malfunctioning
Point B:
Height of coil reverse electromotive force
Contrast with standard wave pattern
Probable cause
Coil reverse electromotive force does not appear or is extremely small.
Short in the coil
Examples of Abnormal Wave Pattern
D
Example 1
Cause of problem
Motor is malfunctioning. (Motor is not operating.)
Wave pattern characteristics
Induced electromotive force from the motor turning does
not appear.
D
Example 2
Cause of problem
Open circuit in the line between the stepper motor and
the engine-ECU.
Wave pattern characteristics
Current is not supplied to the motor coil on the open circuit
side. (Voltage does not drop to 0 V.)
Furthermore, the induced electromotive force waveform
at the normal side is slightly different from the normal
waveform.
Open
circuit
side
Nor-
mal
side
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