Mitsubishi Galant (2004+). Manual - part 1163

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-345

DTC P0155: Heated Oxygen Sensor Heater Circuit (bank 2, sensor 1)

TO PCM

TO PCM

RED-

WHITE

AK302845

RED-WHITE

BR

O

W

N

LEFT BANK HEATED
OXYGEN SENSOR (FRONT)

1

2

3

4

BATTERY

1

3

2

4

125

MFI
RELAY

POWERTRAIN
CONTROL
MODULE (PCM)

B-25

MU802605

Left Bank Heated Oxygen Sensor (front) Heater Circuit

B-23

RED-

WHITE

RED-

WHITE

1

2

3

4

B-17X

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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-346

.

CIRCUIT OPERATION

• Power is supplied from the MFI relay (terminal 

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

• The PCM (terminal No. 125) controls continuity to 

the left bank heated oxygen sensor (front) 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
Left bank heated oxygen sensor heater (front) cur-

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

°C (68°F).

.

MONITOR EXECUTION
Continuous

.

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

AK303070

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AB

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-347

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

.

DTC SET CONDITIONS

Logic Flow Chart

.

DTC SET CONDITIONS

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 (front) 

heater is on.

• Battery positive voltage is at between 11 and 16.5 

volts.

Judgment Criteria

• The left bank heated oxygen sensor (front) heater 

current has continued to be lower than 0.16 
ampere or higher than 7.5 ampere for 4 seconds.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13B-5

.

.

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

• Open or shorted left bank heated oxygen sensor 

(front) heater circuit, or harness damage.

START

END

YES

YES

YES

YES

NO

NO

NO

NO

MALFUNCTION

GOOD

CONTINUOUS

FAILURE FOR 4secs

MONITORING

CONDITIONS

CURRENT < 0.16A

CURRENT > 7.5A

AK302400

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-348

• Open circuit in left bank heated oxygen sensor 

(front) heater.

• Connector damage.

• PCM failed.

DIAGNOSIS

Required Special Tools:

• MD998464: Test Harness

• MB991923: Check Harness

STEP 1. Check harness connector B-25 at the left bank 
heated oxygen sensor (front) 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.

AK303071

1

2

3

4

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE