Mitsubishi 380. Manual - part 630

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-612

STEP 9. Measure the power supply voltage at ECU harness 
side connector B-20.
(1) Disconnect the connector B-20 and measure at the harness 

side.

(2) Using a jumper wire, connect terminal No. 24 to ground.

(3) Measure the voltage between terminals (No. 05) and 

ground.

• Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) 

present?
YES : Replace the ECU. Then confirm that the malfunction 

symptom is eliminated.

NO :  Repair harness wire between MPI relay connector 

B-17X (terminal No. 4) and ECU connector B-20 
(terminal No. 05) because of open circuit. Then 
confirm that the malfunction symptom is eliminated.

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

03DB165A

B-20 HARNESS 

CONNECTOR 

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-613

INSPECTION PROCEDURE 25: Fuel pump system.    

.

CIRCUIT OPERATION

• Battery positive voltage is applied to the fuel 

pump relay 1 (terminal No. 3) from the ignition 

switch-IG.
Ground is provided through terminal No. 2 to 
chassis ground.

03DB166A

CONNECTOR: C-208, C-210

JUNCTION

BLOCK

HARNESS 

CONNECTOR

C-208

C-210

3

4

1

2

3

4

1

2

03DB171A

CONNECTOR: C-29

C-29

1

2

3

4

5

03DB168A

SERVICE

HOLE

FUEL PUMP MODULE

(INCORPORATING FUEL

LEVEL SENSOR (MAIN)

CONNECTOR: D-18

D-18 (GR)

HARNESS

CONNECTOR:

COMPONENT SIDE

03DB174A

CONNECTOR: C-214

JUNCTION

BLOCK

C-214

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

03DB173A

CONNECTOR: C-215

JUNCTION

BLOCK

C-215

03DB170A

CONNECTOR: C-308

C-308

03DB172A

CONNECTOR: C-211

C-211

JUNCTION

BLOCK

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-614

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

position, the battery positive voltage is applied to 
the fuel pump relay 2 (terminal No. 1) from the 
fuel pump relay 1 (terminal No. 1).

• Battery positive voltage is applied to the fuel 

pump relay 2 (terminal No. 3) from the ignition 
switch-IG.

• During cranking and while the engine is running, 

the ECU turns the power transistor in the ECU 
ON to ground the fuel pump relay 2 coil. With this, 
the fuel pump relay turns ON, and the battery 
positive voltage is supplied to the fuel pump from 
the fuel pump relay 2 (terminal No. 4).

.

TROUBLESHOOTING HINTS (The most 
likely causes for this code to be set are:)

• Malfunction of the fuel pump relay.

• Malfunction of the fuel pump.

• Improper connector contact, open or short-circu-

lated harness wire.

• Malfunction of the ECU.

• Refer to component locations GROUP-

70

• Refer to configuration diagrams GROUP-

80

• Refer to circuit diagrams GROUP-

90

DIAGNOSIS

Required Special Tools:

• Diagnostic tool(MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

STEP 1. Check fuel pump operation.
(1) Turn the ignition switch to "ON". Listen for fuel pump 

running for approximately 2 seconds. Pump will 
automatically stop after this time.

NOTE: As the fuel pump is an in-tank type, the fuel pump 
sound is hard to hear. Remove the fuel tank filler tube cap 
and check from the tank inlet.

(2) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the fuel pump operating properly?

YES : That this malfunction is intermittent. Refer to GROUP 

00, How to Use Troubleshooting/Inspection Service 
Points 

− How to Cope with Intermittent Malfunctions 

P.00-14

.

NO :  Go to Step 2.

STEP 2. Check harness connector C-210 at fuel pump relay 
1 and harness connector C-208 at fuel pump relay 2 for 
damage.
Q: Is the harness connector in good condition?

YES : Go to Step 3.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then confirm that the 

malfunction symptom is eliminated.

03DB166A

CONNECTOR: C-208, C-210

JUNCTION

BLOCK

HARNESS 

CONNECTOR

C-208

C-210

3

4

1

2

3

4

1

2

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-615

STEP 3. Check the fuel pump relay 1 and 2.

CAUTION

Because it is not possible to distinguish the top and the 
bottom of the fuel pump relay, inspect it with the triangle 
mark printed on the relay facing upward.
(1) Remove the fuel pump relay 1 and 2.

(2) Check for continuity between the each fuel pump relay 

terminals No. 2 and No. 3.

• There should be continuity. (approximately 70 ohms)

(3) Use jumper wires to connect each fuel pump relay terminal 

No. 3 to the positive battery terminal and terminal No. 2 to 
the negative battery terminal.

(4) Check for continuity between the each fuel pump relay 

terminals No. 1 and No. 4 while connecting and 
disconnecting the jumper wire at the negative battery 
terminal.

• Should be less than 2 ohms. (Negative battery terminal 

connected)

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

nected)

(5) Install the fuel pump relay 1 and 2.

Q: Is the measured resistance normal?

YES : Go to Step 4.
NO :  Replace the fuel pump relay 1 and/or 2. Then confirm 

that the malfunction symptom is eliminated.

03DB166A

CONNECTOR: C-208, C-210

JUNCTION

BLOCK

HARNESS 

CONNECTOR

C-208

C-210

3

4

1

2

3

4

1

2

AK104052

2

3 4

1

FUEL PUMP

RELAY SIDE

CONNECTOR

AB

AK104053

1 2

3 4

AB

FUEL PUMP

RELAY SIDE

CONNECTOR