Mitsubishi Galant 9G. Manual - part 738

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-394

.

CIRCUIT OPERATION

• Power is supplied from the MFI relay (terminal 

No. 4) to the cylinder 2, 3 heated oxygen sensor 
(rear) heater.

• The PCM (terminal No. 137) controls continuity to 

the cylinder 2, 3 heated oxygen sensor (rear) 
heater by turning the power transistor in the PCM 
"ON" and "OFF".

.

TECHNICAL DESCRIPTION

• The PCM checks whether the heater current is 

within a specified range when the heater is ener-
gized.

.

DESCRIPTIONS OF MONITOR METHODS

Cylinder 2, 3 heated oxygen sensor heater (rear) cur-

rent is out of specified range when engine coolant 
temperature is over 20

°C (68°F).

.

MONITOR EXECUTION

Continuous

.

MONITOR EXECUTION CONDITIONS 
(Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored 

in memory for the item monitored below)

• Not applicable

Sensor (The sensor below is determined to be 

normal)

• Engine coolant temperature sensor

.

AK303803AB

CONNECTOR: B-17X

MFI RELAY

B-17X

AK303834AB

CONNECTOR: B-35

B-35 (B)

CYLINDER 2, 3
HEATED OXYGEN
SENSOR (REAR)

AK303059

CONNECTOR: B-23

PCM

AB

AIR CLEANER

B-23

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-395

DTC SET CONDITIONS
Logic Flow Chart

.

Check Conditions

• 60 seconds have elapsed from the start of the 

previous monitoring.

• Engine coolant temperature is higher than 20°C 

(68

°F).

• While the cylinder 2, 3 heated oxygen sensor 

(rear) heater is on.

• Battery positive voltage is between 11 and 16.5 

volts.

Judgment Criteria

• The cylinder 2, 3 heated oxygen sensor (rear) 

heater current has continued to be lower than 
0.16 ampere or higher than 5.0 ampere for 4 sec-
onds.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13A-6

.

.

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

• Open or shorted cylinder 2, 3 heated oxygen sen-

sor (rear) heater circuit, or harness damage.

• Open circuit in cylinder 2, 3 heated oxygen sen-

sor (rear) heater.

• Connector damage.

• Cylinder 2, 3 heated oxygen sensor (rear) failed.

• PCM failed.

START

END

YES

YES

YES

YES

NO

NO

NO

NO

MALFUNCTION

GOOD

CONTINUOUS

FAILURE FOR 4secs

MONITORING

CONDITIONS

CURRENT < 0.16A

CURRENT > 5.0A

AK302027

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-396

DIAGNOSIS

Required Special Tools:

• MD998464: Test Harness

• MB991923: Power Plant ECU Check Harness

STEP 1. Check harness connector B-35 at the cylinder 2, 3 
heated oxygen sensor (rear) for damage.
Q: Is the harness 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 go to Step 12. 

AK303835

1

2

3

4

AB

CONNECTOR: B-35 

B-35 (B)

CYLINDER 2, 3
HEATED OXYGEN
SENSOR (REAR)

HARNESS 
CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-397

STEP 2. Check the cylinder 2, 3 heated oxygen sensor 
(rear).
(1) Disconnect cylinder 2, 3 heated oxygen sensor (rear) 

connector B-35 and connect test harness special tool, 
MD998464, to the connector on the cylinder 2, 3 heated 
oxygen (rear) sensor side.

(2) Measure the resistance between heated oxygen sensor 

connector terminal No. 1 (red clip) and terminal No. 3 (blue 
clip).

Standard value: 11 

− 18 ohms [at 20°C (68°F)]

Q: Is the measured resistance between 11 and 18 ohms [at 

20

°C (68°F)]?

YES : Go to Step 3.
NO :  Replace the cylinder 2, 3 heated oxygen sensor 

(rear). Then go to Step 12.

AK303835

1

2

3

4

AB

CONNECTOR: B-35 

B-35 (B)

CYLINDER 2, 3
HEATED OXYGEN
SENSOR (REAR)

HARNESS 
CONNECTOR:
COMPONENT SIDE

AKX01624

HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR

MD998464

BLUE

RED

AU