Mitsubishi Galant 9G. Manual - part 996

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-284

STEP 2. Check for short circuit to power supply between 
right bank heated oxygen sensor (rear) connector B-08 
(terminal No. 4) and PCM connector B-22 (terminal No. 97).

Q: Is the harness wire in good condition?

YES : Replace the PCM. Then go to Step 3.
NO :  Repair it. Then go to Step 3.

AK303064

1

2

3

4

THROTTLE BODY

RIGHT BANK
HEATED OXYGEN
SENSOR (REAR)

CONNECTOR: B-08

B-08 (GR)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

AK303016

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

CONNECTOR: B-22

B-22 (B)

PCM

AB

HARNESS CONNECTOR: 
COMPONENT SIDE

AIR CLEANER

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-285

STEP 3. 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 6 − 

Other Monitor 

P.13B-6

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0138 set?

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

DTC P0139: Heated Oxygen Sensor Circuit Slow Response (bank 1, sensor 2)

YELLO

W

BLUE

BLA

CK

BLA

CK

AK302842

TO PCM

FROM MFI RELAY

69

97

2

4

3

1

B-22

RIGHT BANK
HEATED OXYGEN
SENSOR (REAR)

POWERTRAIN CONTROL
MODULE (PCM)

4

3

1 2

B-08

MU802665

Right Bank Heated Oxygen Sensor (rear) Circuit

B-21

52

51

53 54 55 56

57

58 59 60 61 62

63

64 65 66 67 68 69

70

71 72 73 74 75

76

77 78 79 80 81 82

83

100

99

92

91

93 94 95

96 97 98

101 102 103 104

105 106 107 108

109 110 111 112 113

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-286

.

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 97) from the output terminal (terminal 
No. 4) of the right bank heated oxygen sensor 
(rear).

• Terminal No. 2 of the right bank heated oxygen 

sensor (rear) is grounded with PCM (terminal No. 
69).

.

TECHNICAL DESCRIPTION

• The output signal of the right bank heated oxygen 

sensor (front) is compensated by the output sig-
nal of the right bank heated oxygen sensor (rear).

• The PCM checks for an open circuit in the right 

bank heated oxygen sensor (rear) output line.

.

DESCRIPTIONS OF MONITOR METHODS

Right bank heated oxygen sensor (rear) output volt-

age does not change during specified go/stop 
operations including fuel cut are repeated.

.

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)

• Heated oxygen sensor heater (front) monitor

• Heated oxygen sensor heater (rear) monitor

• Air/fuel ratio feedback monitor

Sensor (The sensor below is determined to be 

normal)

• Mass airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

• Barometric pressure sensor

.

AK303063

THROTTLE BODY

RIGHT BANK
HEATED OXYGEN
SENSOR (REAR)

CONNECTOR: B-08

B-08 (GR)

AB

AK303013

CONNECTORS: B-21, B-22

PCM

AB

AIR CLEANER

B-22 (B)

B-21 (B)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-287

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• Engine coolant temperature is higher than 76°C 

(169

°F).

• The right bank heated oxygen sensor (front) is 

active.

• The cumulative mass airflow sensor output is 

higher than 1638 g.

• Repeat 3 or more times: drive

*1

, stop

*2

.

Drive

*1

: 

• Engine speed is higher than 1,500 r/min.

• Volumetric efficiency is higher than 40 per-

cent.

• Vehicle speed is higher than 30 km/h (19 

mph).

• A total of more than 10 seconds have 

elapsed with the above mentioned condi-
tions, and more than 2 seconds have 
elapsed with the fuel shut off.

Stop

*2

:

• Vehicle speed is lower than 1.5 km/h (1.0 

mph).

Judgement Criteria

• Change in the output voltage of the right bank 

heated oxygen sensor (rear) is lower than 0.313 
volt.
NOTE: Monitoring stops after fuel has been shut 
off for more than 41 seconds.

.

END

YES

NO

NO

NO

START

MONITORING

CONDITION

YES

MALFUNCTION

GOOD

OUTPUT VOLTAGE 

CHANGE < 0.313 V

GO/STOP OPERATION

FOR SPECIFIED TIMES

YES

AK302399