Mitsubishi Grandis. Manual — part 708
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-83
• When the air-fuel ratio is richer than the
theoretical air-fuel ratio, the cylinder 2, 3 oxygen
sensor (front) outputs a voltage of about 1 V.
When it is leaner than the theoretical air-fuel
ratio, it outputs a voltage of about 0 V.
• In response to the signal, the engine-ECU <M/T>
or engine-A/T-ECU <A/T> controls the fuel
infection amount so that the air-fuel ratio can be
equivalent to the theoretical air-fuel ratio.
TROUBLE JUDGMENT
Check Conditions
• Above 3 minutes later after the engine has
started up.
• The engine coolant temperature is approx. 82°C
or higher.
• The engine speed is 1200 r/min or more.
• The monitoring time is 5 seconds.
Judgment Criteria
• When the cylinder 2, 3 oxygen sensor (front)
output voltage is 0.2 V or less and a power
voltage of 5 V is applied to the cylinder 2, 3
oxygen sensor (front) in the engine-ECU <M/T>
or engine-A/T-ECU <A/T>, the sensor output
voltage is 4.5 V or more.
• To be monitored once per driving cycle.
Check Conditions
• The engine speed is 1200 − 3000 r/min.
• The engine coolant temperature is approx. 60°C
or higher.
• Volumetric efficiency is 20 − 60 %.
• During the air-fuel ratio feedback control.
Judgment Criterion
• When the cylinder 2, 3 oxygen sensor (front)
output frequency is 6 or less for 10 seconds on
the average
PROBABLE CAUSE
• Failed cylinder 2, 3 oxygen sensor (front)
• Open/short circuit in cylinder 2, 3 oxygen sensor
(front) circuit or loose connector contact
• Failed engine-ECU <M/T>
• Failed engine-A/T-ECU <A/T>
DIAGNOSIS PROCEDURE
STEP 1. MUT-III data list
• Refer to Data List Reference Table
a. Item 39: Cylinder 2, 3 oxygen sensor (front)
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-19 cylinder 2, 3
oxygen sensor (front) connector
Q: Is the check result normal?
YES :
Go to Step 3 .
NO :
Repair or replace.
AK300976
1
2
3
4
AC
B-19 (GR)
Connector: B-19
Harness side
connector
Cylinder 2, 3 oxygen
sensor (front)
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-84
STEP 3. Perform resistance measurement at B-19
cylinder 2, 3 oxygen sensor (front) connector.
• Disconnect connector, and measure at harness
side.
• Resistance between terminal No. 2 and earth.
OK: 2
Ω or less
Q: Is the check result normal?
YES :
Go to Step 7 .
NO :
Go to Step 4 .
STEP 4. Connector check: 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 5 .
NO :
Repair or replace.
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
117
118
119
120
Harness side connector
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-85
STEP 5. Check harness between B-19 (terminal
No. 2) cylinder 2, 3 oxygen sensor (front)
connector and C-113 (terminal No. 96)
engine-ECU <M/T> connector or engine-A/T-ECU
<A/T> connector.
• Check earthing line for open circuit and damage.
Q: Is the check result normal?
YES :
Go to Step 6 .
NO :
Repair.
STEP 6. MUT-III data list
• Refer to Data List Reference Table
a. Item 39: Cylinder 2, 3 oxygen sensor (front)
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>.
STEP 7. Perform voltage measurement at B-19
cylinder 2, 3 oxygen sensor (front) connector.
• Use special tool test harness (MB991316) to
connect connector, and measure at pick-up
harness.
• Engine: After warm-up
• Transmission: Neutral <M/T> or P range <A/T>
• Voltage between terminal No. 4 and earth.
OK:
When the engine is 2,500 r/min, the output
voltage should repeat 0 to 0.8 V alternately.
Q: Is the check result normal?
YES :
Go to Step 10 .
NO :
Go to Step 8 .
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
117
118
119
120
Harness side connector
AK300976
1
2
3
4
AC
B-19 (GR)
Connector: B-19
Harness side
connector
Cylinder 2, 3 oxygen
sensor (front)
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-86
STEP 8. Check cylinder 2, 3 oxygen sensor
(front) itself
• Check cylinder 2, 3 oxygen sensor (front) itself
(Refer to
Q: Is the check result normal?
YES :
Go to Step 9 .
NO :
Replace cylinder 2, 3 oxygen sensor (front).
STEP 9. Connector check: C-113 engine-ECU
<M/T> connector or engine-A/T-ECU <A/T>
connector
Q: Is the check result normal?
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
117
118
119
120
Harness side connector
AK300976
1
2
3
4
AC
B-19 (GR)
Connector: B-19
Harness side
connector
Cylinder 2, 3 oxygen
sensor (front)
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