Mitsubishi Galant (2004+). Manual - part 1160

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-333

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

• MD998464: Test Harness

STEP 1. Using scan tool MB991958, check data list item 11: 
Heated Oxygen Sensor Bank 2, Sensor 1 (left front).

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Start the engine and run at idle.

(3) Set scan tool MB991958 to the data reading mode for item 

11, Heated Oxygen Sensor Bank 2, Sensor 1 (left front).

(4) Warm up the engine, 2,500 r/min.

• Output voltage repeats 0.4 volt or less and 0.6 − 1.0 volt 

10 times or more within 10 seconds.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

P.00-6

.

NO :  Go to Step 2. 

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-334

STEP 2. Check the left bank heated oxygen sensor (front).

(1) Disconnect the left bank heated oxygen sensor (front) 

connector B-25 and connect test harness special tool, 
MD998464, to the connector on the left bank heated oxygen 
sensor (front) side.

(2) Warm up the engine until engine coolant temperture 

reaches 80

°C (176°F) or higher.

(3) Perform a tracing for 5 minutes or more with the engine 

speed of 4,500 r/min.

(4) Connect a digital voltage meter between terminal No. 2 

(black clip) and terminal No. 4 (white clip).

(5) While repeatedly revving the engine, measure the left bank 

heated oxygen sensor (front) output voltage.

Standard value: 0.6 

− 1.0 volt

CAUTION

• Be very careful when connecting the jumper wire; 

incorrect connection can damage the oxygen sensor.

• Be careful the heater is broken when voltage of beyond 

8V is applied to the oxygen sensor heater.
NOTE: If the sufficiently high temperature (of approximate 
400

°

C or more) is not reached although the oxygen sensor 

is normal, the output voltage would be possibly low 
although the rich air-fuel ratio. Therefore, if the output volt-
age is low, use a jumper wire to connect the terminal No.1 
(red clip of special tool) and the terminal No. 3 (blue clip of 
special tool) of the oxygen sensor with a (+) terminal and (-) 
terminal of 8 V power supply respectively, then check again.

Q: Is the voltage between 0.6 and 1.0 volt?

YES : Go to Step 3.
NO :  Replace the left bank heated oxygen sensor (front). 

Then go to Step 4.

AK303071

1

2

3

4

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

AKX01624

HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR

MD998464

WHITE

BLACK

AQ

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-335

STEP 3. Check harness connector B-25 at left bank heated 
oxygen sensor (front) and harness connector B-21, B-22 at 
PCM for damage.

Q: Is the harness connector in good condition?

YES : Replace the PCM. Then go to Step 4.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 4.

AK303071

1

2

3

4

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

AK303052

55

56

54 53 52 51

57

62 61 60 59 58

63

69 68 67 66 65 64

70

75 74 73 72 71

76

82 81 80 79 78 77

83

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

CONNECTORS: B-21, B-22

AB

B-21 HARNESS CONNECTOR: 
COMPONENT SIDE

B-22 HARNESS CONNECTOR: 
COMPONENT SIDE

PCM

AIR CLEANER

B-22 (B)

B-21 (B)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-336

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-5

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0153 set?

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

DTC P0154: Heated Oxygen Sensor Circuit No Activity Detected (bank 2, sensor 1)

CAUTION

If DTC P0154 has been set, TCL related DTC 
U1120 is also set. After P0154 has been diag-
nosed, don't forget to erase DTC U1120.

.

Heated Oxygen Sensor Circuit No Activity 
Detected (bank 2, sensor 1) Circuit

• Refer to, DTC P0150 − Left Bank Heated Oxygen 

Sensor (Front) Circuit 

P.13B-300

.

• Refer to, DTC P0202

P.13B-482

, 

P0204

P.13B-503

, P0206

P.13B-524

 

− Injector 

Circuit.

.

CIRCUIT OPERATION

• Refer to, DTC P0152 − Left Bank Heated Oxygen 

Sensor (Front) Circuit 

P.13B-325

.

• Refer to, DTC P0202

P.13B-482

, 

P0204

P.13B-503

, P0206

P.13B-524

 

− Injector 

Circuit.

.

TECHNICAL DESCRIPTION

• The PCM effects air/fuel ratio feedback control in 

accordance with the signals from the left bank 
heater oxygen sensor (front).

• If the left bank heated oxygen sensor (front) has 

deteriorated, corrections will be made by the 
heated oxygen sensor (rear).

• DTC P0154 becomes stored in memory if a fail-

ure is detected in the above air/fuel ratio feed-
back control system.

.

DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (front) output volt-

age does not cross 0.5 volt within specified 
period.

.

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)

• Misfire monitor

Sensor (The sensor below is determined to be 

normal)

• Mass airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

• Barometric pressure sensor

• Throttle position sensor

.