Mitsubishi Lancer Evolution IX. Manual - part 457

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-303

OPERATION

• The battery voltage is applied to the engine con-

trol relay (terminal No. 1 and No. 4).

• The engine-ECU (terminal No. 57) makes the 

power transistor in the unit be in "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).

• The engine-ECU (terminal No. 46, No. 58) is 

grounded to the vehicle body.

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 engine control relay

• Open/short circuit in engine control relay circuit or 

loose connector contact

• Failed engine-ECU

DIAGNOSIS PROCEDURE

NOTE: 

.

*1: L.H. drive vehicles
*2: R.H. drive vehicles

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-12X engine control 
relay connector

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Repair or replace the connector.

STEP 3. Check engine control relay.

• Check engine control relay (Refer to 

P.13A-401

).

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Replace the engine control relay.

STEP 4. Perform voltage measurement at B-12X 
engine control relay connector.

• Remove relay, and measure at relay box side.

• Voltage between terminal No. 1 and earth, also 

between terminal No. 2 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Check intermediate connector A-13

*1

 or 

C-31

*2

, and repair if necessary. If 

intermediate connector is normal, check and 
repair harness between B-12X (terminal No. 
1, No. 2) engine control relay connector and 
battery.

• Check power supply line for 

open/short circuit.

AK305003

2

1

3

4

AB

Connector : B-12X

B-12X

Harness side 
connector

Relay box’s
triangle marks

AK305003

2

1

3

4

AB

Connector : B-12X

B-12X

Harness side 
connector

Relay box’s
triangle marks

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-304

STEP 5. Connector check: C-117 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Repair or replace the connector.

STEP 6. Perform voltage measurement at C-117 
engine-ECU connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: "ON" 

• Voltage between terminal No. 99 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Go to Step 7 .

AK501996

80

87

81

94

85

82

84

93

86

98

99

74

92

73

83

88

91

95

97 96

100

89

78

71

90

76

77

75

72
79

AB

Connector: C-117

C-117 (GR)

C-117 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK501996

80

87

81

94

85

82

84

93

86

98

99

74

92

73

83

88

91

95

97 96

100

89

78

71

90

76

77

75

72
79

AB

Connector: C-117

C-117 (GR)

C-117 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-305

STEP 7. Connector check: C-208 ignition switch 
connector

Q: Is the check result normal?

YES : 

Go to Step 8 .

NO : 

Repair or replace the connector.

AK305251

1

2

3

4

5

6

Harness side connector

Connector: C-208

C-208

<L. H. drive vehicles>

<R. H. drive vehicles>

C-208

AB

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-306

STEP 8. Check ignition switch.

• Check ignition switch (Refer to GROUP 54A − 

Ignition Switch 

− Ignition Switch − Inspection 

P.54A-30

).

Q: Is the check result normal?

YES : 

• Check intermediate connectors C-123, 

C-210 and C-211, then repair if 
necessary. If intermediate connectors 
are normal, check and repair harness 
between C-117(terminal No. 99) 
engine-ECU connector and C-208 
(terminal No. 2) ignition switch 
connector. 

• Check power supply line for 

open/short circuit.

NO : 

Replace the ignition switch.

AK501996

80

87

81

94

85

82

84

93

86

98

99

74

92

73

83

88

91

95

97 96

100

89

78

71

90

76

77

75

72
79

AB

Connector: C-117

C-117 (GR)

C-117 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK305251

1

2

3

4

5

6

Harness side connector

Connector: C-208

C-208

<L. H. drive vehicles>

<R. H. drive vehicles>

C-208

AB