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Mitsubishi Lancer Evolution X. Manual - part 424

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-761

CIRCUIT OPERATION

• Battery positive voltage is applied to the MFI

relay (terminals No. 3, No. 4).

• When the ignition switch is turned to the "ON"

position, battery positive voltage is applied to the
ECM (terminal No. 92). When battery positive
voltage is applied, the ECM turns the power tran-
sistor in the ECM "ON" and grounds the MFI relay
coil. With this, the MFI relay turns "ON" the bat-
tery positive voltage is supplied to the ECM (ter-
minals No. 82) from the MFI relay (terminal No.
2).

• A battery positive voltage is constantly supplied

to the ECM (terminal No. 104) as the backup
power.

• The ECM (terminals No. 81, No. 93) is grounded

to the vehicle body.

COMMENT

• When the ignition switch "ON" signal is input into

the ECM via ETACS-ECU, the ECM turns "ON"
the MFI relay. This causes battery positive volt-
age to be supplied to the ECM, sensor and actua-
tor.

TROUBLESHOOTING HINTS (The most
likely causes for this case)

• Malfunction of the ignition switch.
• Malfunction of the MFI relay.
• Open of shorted power supply and ignition

Switch-IG circuit, harness damage, or connector
damage.

• Malfunction of the ECM.

AK704226

Connector: A-34X

MFI relay

A-34X

AK704235 AB

Connector: B-10

ECM

B-10 (GR)

AK704258 AB

Connector: C-50

C-50 (B)

AK704259AB

Connectors: C-304, C-317

ETACS-ECU

C-304

C-317

AK704352AB

Connector: C-210

C-210

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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DIAGNOSIS

STEP 1. Check harness connector A-34X at MFI relay for
damage.
Q: Is the connector in good condition?

YES : Go to Step 2.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then confirm that the

malfunction symptom is eliminated.

STEP 2. Check the MFI relay.
(1) Remove the MFI relay.
(2) Check for continuity between the MFI relay terminals No. 1

and No. 3.

• There should be continuity.

(3) Use jumper wires to connect MFI relay terminal No. 3 to the

positive battery terminal and terminal No. 1 to the negative
battery terminal.

(4) Check for continuity between the MFI relay terminals No. 4

and No. 2 while connecting and disconnecting the jumper
wire at the negative battery terminal.

• Continuity (2 Ω or less) <Negative battery terminal con-

nected>

• Should be open loop. <Negative battery terminal discon-

nected>

(5) Install the MFI relay.
Q: Is the measured resistance within the specified range?

YES : Go to Step 3.
NO : Replace the MFI relay. Then confirm that the

malfunction symptom is eliminated.

AK703903

MFI relay side
connector

AK703904AB

MFI
relay side
connector

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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STEP 3. Measure the power supply voltage at MFI relay
harness side connector A-34X.
(1) Disconnect the connector A-34X and measure at the

harness side.

(2) Measure the voltage between terminals No. 3, No. 4 and

ground.

• Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts)

present?
YES : Go to Step 4.
NO : Repair harness wire between fusible link (36) and MFI

relay connector A-34X (terminals No. 3, No. 4)
because of open circuit or short circuit to ground.
Then confirm that the malfunction symptom is
eliminated.

STEP 4. Check harness connector B-10 at ECM for
damage.
Q: Is the harness connector in good condition?

YES : Go to Step 5.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then confirm that the

malfunction symptom is eliminated.

STEP 5. Measure the ignition switch-IG signal voltage at
ECM harness side connector B-10.
(1) Disconnect the connector B-10 and measure at the harness

side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 92 and ground.

• Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts)

present?
YES : Go to Step 11.
NO : Go to Step 6.

AK704114

A-34X harness
connector:
component side

82 81 80 79 78 77 76 75 74 73 72 71

94 93 92 91 90 89 88 87 86 85 84 83

99 98 97 96 95

100

101

102

103

104

105

106

112

113

114

109 108

107

110

111

115

116

117

118

AK604044 AD

B-10 harness
connector:
component side

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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STEP 6. Check harness connector C-304, C-317 at
ETACS-ECU connector for damage.
Q: Is the connector in good condition?

YES : Go to Step 7.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then confirm that the

malfunction symptom is eliminated.

STEP 7. Measure the ignition switch-IG signal voltage at
ETACS-ECU harness side connector C-317.
(1) Disconnect the connector C-317 and measure at the

harness side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 6 and ground.

• Voltage should be battery positive voltage

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts)

present?
YES : Go to Step 10.
NO : Go to Step 8.

STEP 8. Check harness connector C-210 ignition switch
connector for damage.
Q: Is the connector in good condition?

YES : Go to Step 9.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then confirm that the

malfunction symptom is eliminated.

STEP 9. Check the ignition switch
Refer to GROUP 54A, Ignition Switch − Inspection − Ignition

Switch Continuity Check

P.54A-31

Q: Are there any abnormalities?

YES : Replace the Ignition Switch. Then confirm that the

malfunction symptom is eliminated.

NO : Repair harness wire between Ignition Switch

connector C-210 (terminal No. 2) and ETACS-ECU
connector C-317 (terminal No. 6) because of open
circuit or short circuit to ground. Then confirm that the
malfunction symptom is eliminated.

6 5

4 3 2 1

1110

151413

9 8

AK704302

C-317 harness
connector:
component side

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