Mitsubishi Grandis. Manual — part 720
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-131
OPERATION
• Power is supplied to the injector (terminal No. 1)
from the engine control relay (terminal No. 1).
• The engine-ECU <M/T> or engine-A/T-ECU
<A/T> (terminal No. 21) makes the power
transistor in the unit be in ON position, and that
makes currents go on the injector (terminal No.
2).
FUNCTION
• The engine-ECU <M/T> or engine-A/T-ECU
<A/T> connector controls the power supply
interval of the injector.
• The fuel injection amount of the injector depends
on the power supply interval.
TROUBLE JUDGMENT
Check Condition
• While engine is running.
Judgment Criterion
• Injector coil surge voltage (battery positive
voltage + 2 V) has not been detected for 2
seconds.
PROBABLE CAUSE
• Failed No. 4 injector
• Open/short circuit in No. 4 injector circuit or loose
connector contact
• Failed engine-ECU <M/T>
• Failed engine-A/T-ECU <A/T>
DIAGNOSIS PROCEDURE
STEP 1. MUT-III actuator test
• Item 04: No. 4 injector
OK: Idling state varies.
Q: Is the check result normal?
YES :
Intermittent malfunction (Refer to GROUP
00
− How to Use
Troubleshooting/Inspection Service Points
).
NO :
Go to Step 2 .
STEP 2. Connector check: B-105 No. 4 injector
connector
Q: Is the check result normal?
YES :
Go to Step 3 .
NO :
Repair or replace.
STEP 3. Check No. 4 injector itself.
• Check No. 4 Injector (Refer to
) itself.
Q: Is the check result normal?
YES :
Go to Step 4 .
NO :
Replace No. 4 injector.
STEP 4. Perform voltage measurement at B-105
No. 4 injector connector.
• Disconnect connector, and measure at harness
side.
• Ignition switch: ON
• Voltage between terminal No. 1 and earth.
OK: System voltage
Q: Is the check result normal?
YES :
Go to Step 6 .
NO :
Go to Step 5 .
AK300978
M
1
2
AM
B-105 (GR)
Harness side connector
Connector: B-105
AK300978
M
1
2
AM
B-105 (GR)
Harness side connector
Connector: B-105
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-132
STEP 5. Connector check: B-15X engine control
relay connector
Q: Is the check result normal?
YES :
Check intermediate connector C-116, and
repair if necessary. If intermediate
connector is normal, check and repair
harness between B-15X (terminal No. 1)
engine control relay connector and B-105
(terminal No. 1) No. 4 injector connector.
• Check power supply line for
open/short circuit and damage.
NO :
Repair or replace.
STEP 6. Connector check: B-15X engine control
relay connector
Q: Is the check result normal?
YES :
Go to Step 7.
NO :
Repair or replace.
STEP 7. Check harness between B-15X (terminal
No. 1) engine control relay connector and B-105
(terminal No. 1) No. 4 injector connector.
NOTE: Before checking harness, check intermediate
connector C-116, and repair if necessary.
• Check power supply line for damage.
Q: Is the check result normal?
YES :
Go to Step 8 .
NO :
Repair.
AK300967
2
1
3
4
AC
Harness side
connector
B-15X
Connector: B-15X
Relay box’s
triangle marks
AK300978
M
1
2
AM
B-105 (GR)
Harness side connector
Connector: B-105
AK300967
2
1
3
4
AC
Harness side
connector
B-15X
Connector: B-15X
Relay box’s
triangle marks
AK300967
2
1
3
4
AC
Harness side
connector
B-15X
Connector: B-15X
Relay box’s
triangle marks
AK300978
M
1
2
AM
B-105 (GR)
Harness side connector
Connector: B-105
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-133
STEP 8. Connector check: C-110 engine-ECU
<M/T> connector or engine-A/T-ECU <A/T>
connector
Q: Is the check result normal?
YES :
Go to Step 9 .
NO :
Repair or replace.
STEP 9. Check harness between B-105 (terminal
No. 2) No. 4 injector connector and C-110
(terminal No. 21) engine-ECU <M/T> connector or
engine-A/T-ECU <A/T> connector.
• Check output line for open/short circuit and
damage.
Q: Is the check result normal?
YES :
Go to Step 10 .
NO :
Repair.
AK305618AB
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Connector: C-110
<L.H. drive vehicles>
<R.H. drive vehicles>
C-110 (GR)
C-110 (GR)
Harness side connector
AK300978
M
1
2
AM
B-105 (GR)
Harness side connector
Connector: B-105
AK305618AB
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Connector: C-110
<L.H. drive vehicles>
<R.H. drive vehicles>
C-110 (GR)
C-110 (GR)
Harness side connector
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-134
STEP 10. Perform signal wave pattern
measurement at C-110 engine-ECU <M/T>
connector or engine-A/T-ECU <A/T> connector
(Using an oscilloscope).
• Engine: Idling
• Transmission: Neutral <M/T> or P range <A/T>
• Voltage between terminal No. 21 and earth.
OK: Waveform should be display on
Inspection procedure using an oscilloscope
(Refer to
Q: Is the check result normal?
YES :
Intermittent malfunction (Refer to GROUP
00
− How to Use
Troubleshooting/Inspection Service Points
).
NO :
Replace engine-ECU <M/T> or
engine-A/T-ECU <A/T>.
AK305618AB
1
2
3
4
5
6
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9
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11
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Connector: C-110
<L.H. drive vehicles>
<R.H. drive vehicles>
C-110 (GR)
C-110 (GR)
Harness side connector
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