Mitsubishi Galant 9G. Manual - part 995

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-280

STEP 5. 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 P0137 set?

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

DTC P0138: Heated Oxygen Sensor Circuit High Voltage (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-281

.

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 is over specified range.

.

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-282

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• 2 seconds or more have passed since the engine 

starting sequence was completed.

Judgment Criteria

• Right bank heated oxygen sensor (rear) output 

voltage has continued to be 1.2 volts or higher for 
2 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: )

• Short circuit in right bank heated oxygen sensor 

(rear) output line.

• Connector damage.

• PCM failed.

START

END

NO

NO

YES

YES

MALFUNCTION

GOOD

2secs HAVE PASSED?

OUTPUT VOLTAGE > 1.2V

NO

YES

MONITORING

CONDITIONS

AK302396

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-283

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

STEP 1. Check harness connector B-08 at right bank 
heated oxygen sensor (rear) and harness connector B-22 
at PCM 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 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