Mitsubishi Colt Ralliart. Manual - part 32

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-82

TROUBLE JUDGMENT

Check Conditions

• After engine starts <M/T>

• Engine coolant temperature is 20°C or higher.

• While oxygen sensor (rear) heater is on <CVT>.

• Battery positive voltage is 11 − 16 V.

• Engine speed is approximately 50 r/min or more 

<CVT>.

Judgment Criterion

• Oxygen sensor (rear) heater currents have con-

tinued to be 0.16 A or lower, or 5.0 A or higher for 
4 seconds.

PROBABLE CAUSES

• Failed oxygen sensor (rear) heater

• Open/short circuit in oxygen sensor (rear) circuit 

or loose connector contact

• Failed engine-ECU <M/T> or engine-CVT-ECU 

<CVT>

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-53 oxygen sensor 
(rear) connector

Q: Is the check result normal?

YES : 

Go to Step 2 .

NO : 

Repair or replace the connector.

STEP 2. Perform resistance measurement at B-53 
oxygen sensor (rear) connector.

• Disconnect connector, and measure at sensor 

side.

• Resistance between terminal No. 3 and No. 4.

OK: 5 

− 30 Ω (at 20°C)

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Replace the oxygen sensor (rear).

AK402019

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2

1

4

Oxygen sensor (rear)

Connector: B-53

B-53 Harness side connector

AC

B-53

AK402019

3

2

1

4

Oxygen sensor (rear)

Connector: B-53

B-53 Harness side connector

AC

B-53

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-83

STEP 3. Perform voltage measurement at B-53 
oxygen sensor (rear) connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: ON

• Voltage between terminal No. 4 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Go to Step 4 .

STEP 4. Connector check: B-106 engine control 
relay connector

AK402019

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2

1

4

Oxygen sensor (rear)

Connector: B-53

B-53 Harness side connector

AC

B-53

3

2

1

4

AK402060

B-106
J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

AK402019

3

2

1

4

Oxygen sensor (rear)

Connector: B-53

B-53 Harness side connector

AC

B-53

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-84

Q: Is the check result normal?

YES : 

Check intermediate connector B-112, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between B-53 (terminal No. 4) 
oxygen sensor (rear) connector and B-106 
(terminal No. 4) engine control relay 
connector.

• Check power supply line for 

open/short circuit.

NO : 

Repair or replace the connector.

STEP 5. Perform voltage measurement at A-08 
engine-ECU connector or engine-CVT-ECU 
connector.

• Disconnect engine-ECU connector or 

engine-CVT-ECU connector, and connect special 
tool power plant ECU check harness 
(MB991987), and then measure the voltage on 
the check connector.

• Ignition switch: ON

• Voltage between terminal No. 79 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 8 .

NO : 

Go to Step 6 .

STEP 6. Connector check: A-08 engine-ECU 
connector or engine-CVT-ECU connector

Q: Is the check result normal?

YES : 

Go to Step 7 .

NO : 

Repair or replace the connector.

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R

AH

A-08

Connector: 

A-08

A-08 Special tool power plant ECU check 
harness

Battery

Engine-ECU <M/T> or
engine-CVT-ECU <CVT>

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R

AG

A-08

Connector: 

A-08

Harness side connector

Battery

Engine-ECU <M/T> or
engine-CVT-ECU <CVT>

Main

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TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-85

STEP 7. Check harness between B-53 (terminal 
No. 3) oxygen sensor (rear) connector and A-08 
(terminal No. 79) engine-ECU connector or 
engine-CVT-ECU connector.

• Check earthing line for open/short circuit.

Q: Is the check result normal?

YES : 

Replace the engine-ECU <M/T> or 

engine-CVT-ECU <CVT>.

NO : 

Repair the damaged harness wire.

STEP 8. Connector check: A-08 engine-ECU 
connector or engine-CVT-ECU connector

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Repair or replace the connector.

AK402019

3

2

1

4

Oxygen sensor (rear)

Connector: B-53

B-53 Harness side connector

AC

B-53

AK402725

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122

123

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127

128

129

72 71

74 73

76 75

R

AG

A-08

Connector: 

A-08

Harness side connector

Battery

Engine-ECU <M/T> or
engine-CVT-ECU <CVT>

AK402725

77

78

79

80

81

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83

84

92

93

94

95

96

97

98

99

85

86

87

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100

101

102

103

104

105

106

115

116

117

118

119

120

121

107

108

109

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112

113

114

130

131

132

133

134

135

136

122

123

124

125

126

127

128

129

72 71

74 73

76 75

R

AG

A-08

Connector: 

A-08

Harness side connector

Battery

Engine-ECU <M/T> or
engine-CVT-ECU <CVT>

Main

Index

Group

TOC