Mitsubishi 380. Manual - part 634

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-628

INSPECTION PROCEDURE 27: Ignition Circuit System.  

AK303271AB

B-118 (GR)

B-102 (GR)

B-101 (GR)

B-117 (GR)

B-103 (GR)

B-114 (GR)

CONNECTOR: B-101, B-102, B-103, B-114,

                         B-117, B-118

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

03DB172A

CONNECTOR: C-211

C-211

JUNCTION

BLOCK

03DB170A

CONNECTOR: C-308

C-308

03DB173A

CONNECTOR: C-215

JUNCTION

BLOCK

C-215

03DB171A

CONNECTOR: C-29

C-29

AK303148

CONNECTOR: A-13

AB

A-13(GR)

AK303097

CONNECTOR: B-32

AB

B-32 (B)

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-629

.

CIRCUIT OPERATION

• The ignition coil is energized by battery positive 

voltage from the ignition switch.

• When the ECU turns off its internal power transis-

tor, battery positive voltage is applied to the igni-
tion power transistor (terminal No. 3) inside the 
ignition coil, causing the ignition power transistor 
to be turned on.

• If the ignition power transistor is turned on, the 

primary circuit of the ignition coil is energized by 
grounding the ignition coil through terminal No. 2, 
causing the primary current to flow to the ignition 
coil.

.

TROUBLESHOOTING HINTS (The most 
likely causes for this case:)

• Malfunction of the ignition coil.

• Malfunction of the ignition power transistor.

• Improper connector contact, open circuit or 

short-circuit 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

STEP 1. Check the ignition coil.
(1) Remove the intake manifold.
(2) Refer to GROUP 16, Ignition System 

− On-vehicle service − 

Ignition Coil Check 

P.16-31

.

Q: Are there any abnormalities?

YES : Replace the ignition coil. Then confirm that the 

malfunction symptom is eliminated. 

NO :  Go to Step 2.

STEP 2. Check harness connectors B-114, B-117, B-118, 
B-102, B-103, B-101 at ignition coil 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.

AK303272AB

B-111 (B)

CONNECTOR: B-111

AK303233

1

2

3

AB

B-118 (GR)

B-102 (GR)

B-101 (GR)

B-117 (GR)

B-103 (GR)

B-114 (GR)

CONNECTOR: B-101, B-102, B-103, B-114,

                         B-117, B-118

HARNESS CONNECTOR:

COMPONENT SIDE

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-630

STEP 3. Measure the power supply voltage at ignition coil 
connectors B-114, B-117, B-118, B-102, B-103, B-101.
(1) Disconnect the connector B-114, B-117, B-118, B-102, 

B-103, B-101 and measure at the harness side.

(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal No. 1 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 5.
NO :  Go to Step 4.

STEP 4. Check for open circuit between ignition switch 
connector C-308 (terminal No. 2) and ignition coil 
connectors B-114, B-117, B-118, B-102, B-103, B-101 
(terminal No. 1).
NOTE: Check harness after checking intermediate connectors 
A-13, B-32, C-29, C-211, C-215 and C-308. If intermediate con-
nectors are damaged, repair or replace them. Refer to GROUP 
00E, Harness Connector Inspection 

P.00E-2

. Then confirm that 

the malfunction symptom is eliminated.

Q: Is the harness wire in good condition?

YES : Repair harness wire between ignition switch 

connector C-308 (terminal No. 2) and capacitor 
connector B-111 (terminal No. 1) because of short 
circuit to ground. Then confirm that the malfunction 
symptom is eliminated.

NO :  Repair it. Then confirm that the malfunction symptom 

is eliminated.

AK303233

1

2

3

AB

B-118 (GR)

B-102 (GR)

B-101 (GR)

B-117 (GR)

B-103 (GR)

B-114 (GR)

CONNECTOR: B-101, B-102, B-103, B-114,

                         B-117, B-118

HARNESS CONNECTOR:

COMPONENT SIDE

1

2

3

AK303273

B-101, B-102, B-103, B-114, 

B-117, B-118 HARNESS 

CONNECTOR: 

COMPONENT SIDE

AB

03DB175A

CONNECTOR: C-308

C-308

1

2

3

4

5

6

HARNESS

CONNECTOR:

COMPONENT SIDE

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-631

STEP 5. Check the circuit at ignition coil harness side 
connectors B-114, B-117, B-118, B-102, B-103, B-101.
(1) Disconnect the connectors B-114, B-117, B-118, B-102, 

B-103, B-101 and measure at the harness side.

(2) Crank the engine.

(3) Measure the voltage between terminal No. 3 and ground.

NOTE: The average voltage through an analog voltmeter is 
described in this service manual (because the average volt-
age is too stable to be shown on a digital voltmeter).

• Voltage should be 0.3 and 3.0 volts.

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

Q: Is the measured voltage between 0.3 and 3.0 volts?

YES : Go to Step 8.
NO :  Go to Step 6.

STEP 6. Check connector B-20 at ECU 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.

AK303233

1

2

3

AB

B-118 (GR)

B-102 (GR)

B-101 (GR)

B-117 (GR)

B-103 (GR)

B-114 (GR)

CONNECTOR: B-101, B-102, B-103, B-114,

                         B-117, B-118

HARNESS CONNECTOR:

COMPONENT SIDE

1

2

3

AK303275

B-101, B-102, B-103, B-114, 

B-117, B-118 HARNESS 

CONNECTOR: 

COMPONENT SIDE

AB

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER