Mitsubishi Colt Ralliart. Manual - part 739

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-281

Inspection Procedure 20: Poor A/C Performance

COMMENT ON TROUBLE SYMPTOM

• Failure is possibly caused by short/overcharged 

A/C refrigerant, failed A/C control system, failed 
fan control system, or other faults.

PROBABLE CAUSES

• Short- or overcharged A/C refrigerant

• Failed A/C compressor relay

• Failed cooling fan control relay

• Failed A/C-ECU

• Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q: Is the diagnosis code output?

YES : 

Inspection chart for diagnosis code (Refer 

to 

P.13B-18

).

NO : 

Go to Step 2 .

STEP 2. Check A/C compressor magnet clutch 
operation.

• Engine: Idling

• A/C set temperature:

Maximum Cool when temperature in cabin is 

25

°C or more

Maximum Hot when temperature in cabin is 25

°C 

or less

OK:

Magnet clutch active (when A/C is ON)
Magnet clutch inactive (when A/C is OFF)

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Go to Step 3 .

STEP 3. M.U.T.-III data list

• Item 49: A/C relay

a. Engine: Idling
b. A/C set temperature:

Maximum Cool when temperature in cabin is 

25

°C or more

Maximum Hot when temperature in cabin is 

25

°C or less

OK: 

ON (when A/C is ON)
OFF (when A/C is OFF)

Q: Is the check result normal?

YES : 

Check A/C system, Refer to GROUP 55B 

− 

Troubleshooting 

− Check Chart for 

Diagnosis Code 

P.55B-3

 )

NO : 

Check A/C compressor relay system (Refer 
to Inspection Procedure 24 

P.13B-317

).

STEP 4. M.U.T.-III actuator test

• Refer to Actuator Test Reference Table 

P.13B-344

a. Item 20: Cooling fan motor (HI)
b. Item 21: Cooling fan motor (LO)

Q: Are the check results normal?

YES : 

Check charged amount of A/C refrigerant 

(Refer to GROUP 55A 

− On-vehicle Service 

− Check The Refrigerant Level 

P.55A-50

).

NO : 

Check fan control relay system (Refer to 
Inspection Procedure 23 

P.13B-303

).

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TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-282

Inspection Procedure 21: Engine-ECU Power Supply, Engine Control Relay, Ignition Switch-IG1 
System

AK600600

R

92 93 94 95969798

77 78 79 808182838485868788899091

99

100

107 108 109 110 111112113114115116117118119120121
122 123 124 125126127128129130131132133134135136

101102103104105106

71 72

73 74

75 76

3

1

2

4

1 2 3
4 5 6

B-141

B-106

A-08

R

IG2

ST

LOCK

ACC

IG1

16

1

20A

38

7.5A

Fusible link

Ignition switch

3

2

J/B

122

75

2

76

B

B

3

B-110

B-112

B-112

B-112

B-108

B-129

82

Engine 
control 
relay

3

1

1

4

2

107

Battery
backup

92

19

23

6

77

Power
source

9

R

R-B

B-O

L-B

G

R

R

Power Supply And Ignition Switch-IG Circuit

43

10A

Wire colour code
B: Black  LG: Light green  G: Green  L: Blue  W: White  Y: Yellow  SB: Sky blue  BR: Brown  O: Orange  GR: Gray
R: Red  P: Pink  V: Violet  P: Purple

Engine-ECU

A-31
 J/C

A-30
 J/C

AB

GND

GND

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-283

OPERATION

• The battery voltage is applied to the engine con-

trol relay (terminal No. 1 and No. 3).

• The engine-ECU (terminal No. 107) makes the 

power transistor in the unit be ON position and 
makes currents go on the engine control relay 
coil, and that makes the relay be in ON position.

• When the engine control relay is in ON position, 

the battery voltage is supplied to the 
engine-ECU, the sensor and the actuator from 
the engine control relay (terminal No. 4).

FUNCTION

• When the ignition switch ON signal is input to the 

engine-ECU, the engine-ECU places the engine 
control relay in the ON position. Accordingly, the 
battery voltage is supplied to the engine-ECU, 
sensor and actuator.

PROBABLE CAUSES

• Failed battery

• Failed engine control relay

• Failed ignition switch

• Open/short circuit in or damage to the engine 

control relay circuit or loose connector contact

• Open/short circuit in or damage to the ignition 

switch-IG1 circuit or loose connector contact

• Open/short circuit in or damage to the 

engine-ECU circuit or loose connector contact

• Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery voltage.

• Measure battery voltage during cranking.

OK: 8 V or more

Q: Is the check result normal?

YES : 

Go to Step 2 .

NO : 

Check battery (Refer to GROUP 54A 

− 

Battery 

− On-vehicle Service − Battery Test 

P.54A-5

).

STEP 2. Connector check: B-106 engine control 
relay connector

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Repair or replace.

STEP 3. Check engine control relay.

• Check engine control relay (Refer to 

P.13B-363

).

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Replace engine control relay.

3

2

1

4

AK402084

J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-284

STEP 4. Perform voltage measurement at B-106 
engine control relay connector.

•

Remove relay, and measure at connector side.

• Ignition switch: ON

• Voltage between terminal No. 1 and earth, also 

between No. 3 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Check intermediate connector B-108, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between battery and B-106 
(terminal No. 1 and No. 3) engine control 
relay connector.

• Check power supply line for 

open/short circuit.

STEP 5. Connector check: A-08 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Repair or replace.

3

2

1

4

AK402084

J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

AK402725

77

78

79

80

81

82

83

84

92

93

94

95

96

97

98

99

85

86

87

88

89

90

91

100

101

102

103

104

105

106

115

116

117

118

119

120

121

107

108

109

110

111

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

AI

A-08

Connector: 

A-08

A-08 Special tool power plant ECU check 
harness

Engine-ECU

Battery

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