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 

P.13A-363

.

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 

P.00-5

).

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

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113

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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 

P.13A-363

.

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 

P.00-5

).

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 

P.13A-391

).

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)