Mitsubishi Galant (2004+). Manual - part 858

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-249

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• 3 minutes or more have passed since the engine 

starting sequence was completed.

• Cylinder 1, 4 heated oxygen sensor (rear) signal 

voltage has continued to be 0.15 volt or lower.

• Engine coolant temperature is higher than 76°C 

(169

°F).

• Engine speed is higher than 1,200 r/min.

• Volumetric efficiency is higher than 25 percent.

• Monitoring time: 7 seconds.

START

V

F

 > =4.5V

2secs HAVE

PASSED

YES

YES

YES

NO

NO

NO

MALFUNCTION

MONITORING

CONDITIONS

YES

NO

MONITORING

CONDITIONS

+5V ON

AK302025

V

F

 < 0.15V

10secs HAVE

PASSED

YES

YES

NO

NO

END

MALFUNCTION

GOOD

MODULATE A/F CONDITION TO RICH

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-250

Judgment Criteria

• Input voltage supplied to the PCM interface circuit 

is higher than 4.5 volts when 5 volts is applied to 
the cylinder 1, 4 heated oxygen sensor (rear) out-
put line via a resistor.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13A-5

.

.

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

• Cylinder 1, 4 heated oxygen sensor (rear) failed.

• Open or shorted circuit in cylinder 1, 4 heated 

oxygen sensor (rear) output line or harness dam-
age.

• Open circuit in cylinder 1, 4 heated oxygen sen-

sor (rear) ground line or harness damage.

• Connector damage.

• PCM failed.

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

• MB991923: Power Plant ECU Check Harness

STEP 1. Using scan tool MB991958, check data list item 69: 
Cylinder 1, 4 Heated Oxygen Sensor (rear).

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 

69, Cylinder 1, 4 Heated Oxygen Sensor (rear).

• Warming up the engine. When the engine is revved, the 

output voltage should repeat 0 volt and 0.6 to 1.0 volt 
alternately.

(4) 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.

AK303804AB

MB991910

DATA LINK
CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-251

STEP 2. Measure the sensor output voltage at cylinder 1, 4 
heated oxygen sensor (rear) connector B-38 by 
backprobing
(1) Do not disconnect the connector B-38.
(2) Start the engine and run at idle.

(3) Measure the voltage between terminal No. 4 and ground by 

backprobing.

• Warming up the engine. When the engine is revved, the 

output voltage should repeat 0 volt and 0.6 to 1.0 volt 
alternately.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?

YES : Go to Step 3.
NO :  Go to Step 7.

AK303826

1

2

3

4

AB

HARNESS 
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-38

B-38 (B)

CYLINDER 1, 4
HEATED OXYGEN
SENSOR (REAR)

AKX01532AG

3

1 2

4

B-38 HARNESS 
CONNECTOR: 
HARNESS SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-252

STEP 3. Measure the sensor output voltage at PCM 
connector B-22 by using power plant ECU check harness 
special tool MB991923.
(1) Disconnect the all PCM connectors and connect power 

plant ECU check harness special tool MB991923 between 
the separated connectors.

(2) Start the engine and run at idle.

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

AK202956

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

AB

POWER PLANT ECU 
CHECK HARNESS CONNECTOR

MB991923

PCM