Mitsubishi Grandis. Manual — part 700
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-51
FUNCTION
• The engine-ECU <M/T> or engine-A/T-ECU
<A/T> effects air-fuel ratio feedback control in
accordance with the signals from the oxygen
sensor (front).
• If the oxygen sensor (front) has deteriorated,
corrections will be made by the oxygen sensor
(rear).
• Diagnosis code P0125 becomes stored in
memory if a failure is detected in the above
air/fuel ratio feedback control system.
TROUBLE JUDGMENT
Check Conditions
• The engine coolant temperature approximately
76
°C or more.
• Within the range of air-fuel ratio feedback
operation.
• Not in low speed operation.
Judgment Criterion
• The oxygen sensor output voltage is not deviated
from 0.5 V for 30 seconds.
PROBABLE CAUSE
• Failed oxygen sensor (front)
• Harness damage in oxygen sensor (front) circuit
or loose connector contact
• Failed oxygen sensor (rear)
NOTE: When the oxygen sensor (front) begins to
deteriorate, the oxygen sensor output voltage will
deviate from the voltage when the sensor was new
(normally 0.5 volt at stoichiometric ratio). This
deviation will be corrected by the oxygen sensor
(rear).If the oxygen sensor (rear) responds poorly
because it has deteriorated, it will improperly correct
the oxygen sensor (front). Thus, even when closed
loop control is being effected, the fluctuation of the
oxygen sensor (front) output voltage decreases,
without intersecting with 0.5 volt. As a result, there is
a possibility of diagnosis code P0125 becoming
registered.
• Failed fuel system
• Failed exhaust system
• Failed engine-ECU <M/T>
• Failed engine-A/T-ECU <A/T>
DIAGNOSIS PROCEDURE
STEP 1. MUT-III diagnosis code
Q: Is any other diagnosis code than P0170 or P0173
output?
YES :
Inspection chart for diagnosis code (Refer
to
NO :
Go to Step 2 .
STEP 2.MUT-III data list
• Refer to Data List Reference Table
a. Item 12: Air flow sensor
b. Item 21: Engine coolant temperature sensor
c. Item 59: Cylinder 1, 4 oxygen sensor (front)
d. Item 69: Cylinder 2, 3 oxygen sensor (rear)
Q: Are the check results normal?
YES :
Go to Step 3 .
NO :
Perform the diagnosis code classified check
procedure for the sensor that has shown an
abnormal data valve (Refer to Inspection
Chart for Diagnosis Code
STEP 3: MUT-III data list
• Refer to Data List Reference Table
a. Item 25: Barometric pressure sensor
Q: Are the check results normal?
YES :
Go to Step 4 .
NO :
Replace engine-ECU <M/T> or
engine-A/T-ECU <A/T>.
STEP 4.Check for intake of air from intake hose
and inlet manifold.
Q: Is the check result normal?
YES :
Go to Step 5 .
NO :
Repair.
STEP 5.Check for leakage of exhaust emission
from exhaust manifold.
Q: Is the check result normal?
YES :
Go to Step 6 .
NO :
Repair.
STEP 6.Check throttle body (throttle valve
portion) for contamination.
Q: Is the check result normal?
YES :
Go to Step 7 .
NO :
Clean throttle body (throttle valve portion)
(Refer to
).
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-52
STEP 7. Connector check: B-22 cylinder 1, 4
oxygen sensor (front) connector, C-113
engine-ECU <M/T> connector or engine-A/T-ECU
<A/T> connector.
Q: Is the check result normal?
YES :
Go to Step 8 .
NO :
Repair or replace.
STEP8. Check cylinder 1, 4 oxygen sensor (front)
itself.
• Check cylinder 1, 4 oxygen sensor (front) itself
(Refer to
Q: Is the check result normal?
YES :
Go to Step 9 .
NO :
Replace cylinder 1, 4 oxygen sensor (front).
STEP 9. Check harness between B-22 (terminal
No. 4) cylinder 1, 4 oxygen sensor (front)
connector and C-113 (terminal No. 109)
engine-ECU <M/T> connector or engine-A/T-ECU
<A/T> connector.
• Check output line for damage.
Q: Is the check result normal?
YES :
Go to Step 10 .
NO :
Repair.
AK300973
1
2
3
4
AB
ƒn
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-53
STEP 10. Connector check: B-19 cylinder 2, 3
oxygen sensor (front) connector, C-113
engine-ECU <M/T> connector or engine-A/T-ECU
<A/T> connector.
Q: Is the check result normal?
YES :
Go to Step 11 .
NO :
Repair or replace.
STEP 11. Check cylinder 2, 3 oxygen sensor
(front) itself.
• Check cylinder 2, 3 oxygen sensor (front) itself
Q: Is the check result normal?
YES :
Go to Step 12 .
NO :
Replace cylinder 2, 3 oxygen sensor (front).
AK300976
1
2
3
4
AC
B-19 (GR)
Connector: B-19
Harness side
connector
Cylinder 2, 3 oxygen
sensor (front)
AK305616AB
Connector: C-113
<L.H. drive vehicles>
<R.H. drive vehicles>
C-113 (GR)
C-113 (GR)
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
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112
113
114
115
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117
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119
120
Harness side connector
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-54
STEP 12. Check harness between B-19 (terminal
No. 4) cylinder 2, 3 oxygen sensor (front)
connector and C-113 (terminal No. 108)
engine-ECU <M/T> connector or engine-A/T-ECU
<A/T> connector.
• Check output line for damage.
Q: Is the check result normal?
YES :
Go to Step 13 .
NO :
Repair.
STEP 13. Connector check: Injector connector
a. B-101 (No.1 injector connector)
b. B-102 (No.2 injector connector)
c. B-104 (No.3 injector connector)
d. B-105 (No.4 injector connector)
Q: Is the check result normal?
YES :
Go to Step 14 .
NO :
Repair or replace.
STEP 14. Check injector itself.
• Check Injector itself (Refer to
Q: Is the check result normal?
YES :
Go to Step 15 .
NO :
Replace injector.
AK300976
1
2
3
4
AC
B-19 (GR)
Connector: B-19
Harness side
connector
Cylinder 2, 3 oxygen
sensor (front)
AK305616AB
Connector: C-113
<L.H. drive vehicles>
<R.H. drive vehicles>
C-113 (GR)
C-113 (GR)
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
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118
119
120
Harness side connector
AK300978
M
1
2
AG
Harness side connector
Connectors: B-101, B-102, B-104, B-105
B-101 (GR) B-102 (GR)
B-105 (GR)
B-104 (GR)
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