Mitsubishi Galant 9G. Manual - part 1025

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-400

STEP 4. Test the OBD-II drive cycle.

(1) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function 

− OBD-II Drive Cycle − Procedure 4 − 

Heated Oxygen Sensor Monitor 

P.13B-6

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0159 set?

YES : Retry the troubleshooting.
NO :  The inspection is complete.

DTC P0161: Heated Oxygen Sensor Heater Circuit (bank 2, sensor 2)

RED-

WHITE

RED-

WHITE

AK400906

BLUE-RED

LEFT BANK HEATED
OXYGEN SENSOR (REAR)

B-17X

1

2

3

4

BATTERY

1

3

2

4

137

MFI
RELAY

POWERTRAIN
CONTROL
MODULE (PCM)

B-24

MU802665

Left Bank Heated Oxygen Sensor (rear) Heater Circuit

B-23

1

2

3

4

1

2

3

4

121 122 123 124 125 126 127

128 129 130 131 132 133

134 135 136 137 138 139 140

141 142 143 144 145 146

147 148 149 150 151 152 153

RED

RED-WHITE

TO PCM

TO PCM TO PCM

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-401

.

CIRCUIT OPERATION

• Power is supplied from the MFI relay (terminal 

No. 4) to the left bank heated oxygen sensor 
(rear) heater.

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

the left bank heated oxygen sensor (rear) heater 
by turning the power transistor in the PCM "ON" 
and "OFF".

.

BACKGROUND

• The PCM checks whether the heater current is 

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

.

DESCRIPTIONS OF MONITOR METHODS

Left bank heated oxygen sensor heater (rear) current 

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

1

2

3

4

1

2

3

4

1

2

3

4

1

2

3

4

AK303014

CONNECTOR: B-17X

MFI RELAY

MFI RELAY

FRONT OF VEHICLE

B-17X

AB

AK303079

CONNECTOR: B-24

AB

LEFT BANK
HEATED OXYGEN
SENSOR (REAR)

B-24 (GR)

AK303059

CONNECTOR: B-23

PCM

AB

AIR CLEANER

B-23

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-402

.

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 left bank heated oxygen sensor (rear) 

heater is on.

• Battery positive voltage is between 11 and 16.5 

volts.

Judgment Criteria

• The left bank heated oxygen sensor (rear) heater  

current has continued to be lower than 0.16 
ampere or higher than 5.0 ampere for 4 seconds.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13B-6

.

.

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

• Open or shorted left bank heated oxygen sensor 

(rear) heater circuit, or harness damage.

• Open circuit in left bank heated oxygen sensor 

(rear) heater.

• Connector damage.

• Left bank 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

AK302401

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-403

DIAGNOSIS

Required Special Tools:

• MB991316: Test Harness

• MB991923: Power Plant ECU Check Harness

STEP 1. Check harness connector B-24 at the left bank 
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. 

1

2

3

4

AK303079

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-24

AB

LEFT BANK
HEATED OXYGEN
SENSOR (REAR)

B-24 (GR)