Mitsubishi Galant (2004+). Manual - part 1152

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-301

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 91) from the output terminal (terminal
No. 4) of the left bank heated oxygen sensor
(front).

• Terminal No. 2 of the left bank heated oxygen

sensor (front) is grounded with or PCM (terminal
No. 69).

TECHNICAL DESCRIPTION

• The left bank heated oxygen sensor (front)

detects the concentration of oxygen in the
exhaust gas; it converts that data to voltage, and
sends it to the PCM.

• When the left bank heated oxygen sensor (front)

begins to deteriorate, the heated oxygen sensor
signal response deteriorates also.

• The PCM forcibly varies the air/fuel mixture to

make it leaner and richer, and checks the
response speed of the left bank heated oxygen
sensor (front). In addition, the PCM also checks
for an open circuit in the left bank heated oxygen
sensor (front) output line.

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

• Misfire monitor

• Fuel system 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

• Accelerator pedal position sensor

AK303070

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AK303013

CONNECTORS: B-21, B-22

PCM

AIR CLEANER

B-22 (B)

B-21 (B)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-302

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

• 3 minutes or more have passed since the starting

sequence was completed.

• Left bank heated oxygen sensor (front) signal

voltage has continued to be 0.2 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

> =4.5V

2secs HAS PASSED

YES

MALFUNCTION

MONITORING

CONDITIONS

YES

MONITORING

CONDITIONS

+5V ON

AK302397

< 0.2V

10secs HAS PASSED

YES

END

MALFUNCTION

GOOD

MODULATE A/F CONDITION TO RICH

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-303

Judgment Criteria

• Input voltage supplied to the PCM interface circuit

is higher than 4.5 volts when 5 volts is applied to
the left bank heated oxygen sensor (front) output
line.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 6

− Other Monitor.

P.13B-5

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

• Left bank heated oxygen sensor (front) deterio-

rated.

• Open or shorted circuit in left bank heated oxy-

gen sensor (front) output line, or harness dam-
age.

• Open circuit in left bank heated oxygen sensor

(front) 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 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).

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

output voltage should be 0.6 to 1.0 volt.

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

output voltage should repeat 0.4 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.

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-304

STEP 2. Measure the sensor output voltage at left bank
heated oxygen sensor (front) connector B-25 by
backprobing

(1) Do not disconnect the connector B-25.
(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 2,500 r/min,

the output voltage should repeat 0 to 0.8 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.

AK303071

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

HARNESS
CONNECTOR:
COMPONENT SIDE

AKX01532AE

1 2

B-25 HARNESS
CONNECTOR:
HARNESS SIDE

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