Mitsubishi Galant (2004+). Manual - part 1166

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-357

STEP 10. Check for harness damage between left bank 
heated oxygen sensor (front) connector B-25 (terminal No. 
3) and PCM connector B-23 (terminal No. 125).

Q: Is the harness wire in good condition?

YES : Go to Step 11.
NO :  Repair it. 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

127 126 125 124 123 122 121

133 132 131 130 129 128

140 139 138 137 136 135 134

146 145 144 143 142 141

153 152 151 150 149 148 147

AK303058

HARNESS CONNECTOR: 
COMPONENT SIDE

CONNECTOR: B-23

B-23

PCM

AB

AIR CLEANER

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-358

STEP 11. Check the trouble symptoms.

(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-5

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0155 set?

YES : Replace the PCM. Then go to Step 12.
NO :  It can be assumed that this malfunction is intermittent. 

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

P.00-6

 .

STEP 12. 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-5

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0155 set?

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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-359

DTC P0156: Heated Oxygen Sensor Circuit (bank 2, sensor 2)

GREEN

BLUE

BLA

CK

AK302846

TO PCM

FROM MFI RELAY

69

96

2

4

3

1

LEFT BANK
HEATED OXYGEN
SENSOR (REAR)

POWERTRAIN CONTROL
MODULE (PCM)

B-24

MU802665

B-22

Left Bank Heated Oxygen Sensor (rear) Circuit

B-21

1

2

3

4

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-360

.

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 96) from the output terminal (terminal 
No. 4) of the left bank heated oxygen sensor 
(rear).

• Terminal No. 2 of the left bank heated oxygen 

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

.

TECHNICAL DESCRIPTION

• The output signal of the left bank heated oxygen 

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

• The PCM checks for an open circuit in the left 

bank heated oxygen sensor (rear) output line.

.

DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (rear) circuit is 

switched to 5 volts intentionally when oxygen 
sensor output is low, and detects the malfunction 
if the output voltage changes to equal or greater 
than 4.5 volts. The above procedure is repeated 
when oxygen sensor is inactive.

.

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

.

AK303079

CONNECTOR: B-24

AB

LEFT BANK
HEATED OXYGEN
SENSOR (REAR)

B-24 (GR)

AK303013

CONNECTORS: B-21, B-22

PCM

AB

AIR CLEANER

B-22 (B)

B-21 (B)