Mitsubishi Galant 9G. Manual - part 723

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-334

STEP 3. Check harness connector B-36 at cylinder 2, 3
heated oxygen sensor (front) and harness connector B-21,
B-22 at PCM for damage.
Q: Is the harness connector in good condition?

YES : Replace the PCM. Then go to Step 4.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then go to Step 4.

AK303830

CONNECTOR: B-36

B-36 (GR)

CYLINDER 2, 3
HEATED OXYGEN
SENSOR (FRONT)

HARNESS
CONNECTOR:
COMPONENT SIDE

AK303052

54 53 52 51

62 61 60 59 58

69 68 67 66 65 64

75 74 73 72 71

82 81 80 79 78 77

104

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

CONNECTORS: B-21, B-22

B-21 HARNESS CONNECTOR:
COMPONENT SIDE

B-22 HARNESS CONNECTOR:
COMPONENT SIDE

PCM

AIR CLEANER

B-22 (B)

B-21 (B)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-335

STEP 4. 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 4 −

Heated Oxygen Sensor Monitor

P.13A-6

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0153 set?

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

DTC P0154: Cylinder 2, 3 Heated Oxygen Sensor No Activity Detected (sensor 1)

CAUTION

If DTC P0154 has been set, TCL related DTC
U1120 is also set. After P0154 has been diag-
nosed, don't forget to erase DTC U1120.

Cylinder 2, 3 Heated Oxygen Sensor
Circuit No Activity Detected (sensor 1)
Circuit

• Refer to DTC P0150 − Cylinder 2, 3 Heated Oxy-

gen Sensor (Front) Circuit

P.13A-299

• Refer to DTC P0202 − Injector Circuit-cylinder 2

P.13A-474

• Refer to DTC P0203 − Injector Circuit-cylinder 3

P.13A-484

CIRCUIT OPERATION

• Refer to DTC P0150 − Cylinder 2, 3 Heated Oxy-

gen Sensor (Front) Circuit

P.13A-299

• Refer to DTC P0202 − Injector Circuit-cylinder 2

P.13A-474

• Refer to DTC P0203 − Injector Circuit-cylinder 3

P.13A-484

TECHNICAL DESCRIPTION

• The PCM effects air/fuel ratio feedback control in

accordance with the signals from the cylinder 2, 3
heater oxygen sensor (front).

• If the cylinder 2, 3 heated oxygen sensor (front)

has deteriorated, corrections will be made by the
cylinder 2, 3 heated oxygen sensor (rear).

• DTC P0154 becomes stored in memory if a fail-

ure is detected in the above air/fuel ratio feed-
back control system.

DESCRIPTIONS OF MONITOR METHODS

Cylinder 2, 3 heated oxygen sensor (front) output

voltage does not cross 0.5 volt within specified
period.

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)

• Misfire 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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-336

DTC SET CONDITIONS
Logic Flow Chart

Check Conditions

• 20 seconds or more have passed since the

engine starting sequence was completed.

• Engine coolant temperature is higher than 60°C

(140

° F).

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

• Volumetric efficiency is higher than 30 percent.

• Throttle position sensor output voltage is lower

than 4 volts.

• Except while fuel is being shut off.

• Monitoring time: 30 seconds.

Judgment Criteria

• Cylinder 2, 3 heated oxygen sensor (front) output

voltage does not get across 0.5 volt within about
30 seconds.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 6

− Other Monitor

P.13A-6

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

• Cylinder 2, 3 heated oxygen sensor (front) deteri-

orated.

• Harness damage in cylinder 2, 3 heated oxygen

sensor (front) output line.

• Cylinder 2, 3 heated oxygen sensor (rear) deteri-

orated.

HEATED OXYGEN SENSOR (FRONT)

OUTPUT VOLTAGE CROSSES 0.5V?

START

END

YES

Yes

YES

MALFUNCTION

GOOD

30secs HAVE PASSED?

MONITORING

CONDITIONS

AK203999

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-337

NOTE: When the cylinder 2, 3 heated oxygen
sensor (front) begins to deteriorate, the heated
oxygen sensor output voltage will deviate from
the voltage when the sensor was new (normally
0.5 volt at stoichiometric ratio). This deviation will
be corrected by the cylinder 2, 3 heated oxygen
sensor (rear).
If the cylinder 2, 3 heated oxygen sensor (rear)
responds poorly because it has deteriorated, it
will improperly correct the cylinder 2, 3 heated
oxygen sensor (front). Thus, even when closed
loop control is being effected, the fluctuation of
the cylinder 2, 3 heated oxygen sensor (front)
output voltage decreases, without intersecting
with 0.5 volt. As a result, there is a possibility of
DTC P0154 becoming registered.

• Open circuit in cylinder 2, 3 injector.

• Harness damage in cylinder 2, 3 injector circuit.

• Connector damage.

• PCM failed.

• Exhaust leak.

• Air drawn in from gaps in gasket, seals, etc.

• Incorrect fuel pressure.

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

• MB991316: Test Harness

STEP 1. Using scan tool MB991958, check data list item 59:
Cylinder 2, 3 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

59, Cylinder 2, 3 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 : Go to Step 2.
NO : Refer to DTC P0156

− Cylinder 2, 3 Heated Oxygen

Sensor Circuit (sensor 2)

P.13A-357

, DTC P0157

−

Cylinder 2, 3 Heated Oxygen Sensor Circuit Low
Voltage (sensor 2)

P.13A-375