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Mitsubishi Galant 9G. Manual - part 687

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-190

DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

TECHNICAL DESCRIPTION

• The PCM checks the time for the cooling water

temperature to reach the judgment temperature.

DESCRIPTIONS OF MONITOR METHODS

Engine coolant temperature does not reach 77

°C

(171

°F) within specified period after cold start.

MONITOR EXECUTION

Once per driving cycle

MONITOR EXECUTION CONDITIONS
(Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored

in memory for the item monitored below)

• Not applicable

Sensor (The sensor below is determined to be

normal)

• Mass airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

DTC SET CONDITIONS
Logic Flow Chart

START

END

YES

MALFUNCTION

GOOD

TIME HAVE PASSED

AFTER STARTING?*

ENGINE COOLANT TEMP.

>=77˚C (171˚F)

*: See DTC SET CONDITIONS-JUDGMENT CRITERIA

MONITORING

CONDITIONS?

YES

AK204044

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

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Check Conditions

• Engine coolant temperature is between −10°C

(14

°F) and 77°C (171°F) when the engine is

started.

• The engine coolant temperature − intake air tem-

perature is 5

°C (9°F) or less when the engine is

started.

• The intake air temperature when the engine is

started

− intake air temperature is 5°C (9°F) or

less.

• The total time of the mass airflow sensor output

whose state is below 10 g/sec within 600 sec-
onds.

Judgment Criteria

• The time for the engine coolant temperature to

rise to 77

°C (171°F) takes longer than approxi-

mately 11 to 32 minutes.

OBD-II DRIVE CYCLE PATTERN

None.

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

• The thermostat is faulty.

• PCM failed.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

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DIAGNOSIS

STEP 1. Check the cooling system.
Refer to GROUP 14, Engine Cooling Diagnosis

P.14-3

Q: Is the cooling system normal?

YES : Replace the PCM. Then check that the DTC P0128

does not reset.

NO : Repair it. Then check that the DTC P0128 does not

reset.

DTC P0130: Cylinder 1, 4 Heated Oxygen Sensor Circuit (sensor 1)

100

93 94 95

96 97 98

101 102 103 104

105 106 107 108

109 110 111 112 113

53 54 55 56

58 59 60 61 62

64 65 66 67 68 69

71 72 73 74 75

77 78 79 80 81 82

AK303819

BLA

BLUE

BLA

TO PCM

FROM MFI RELAY

PINK

CYLINDER 1, 4
HEATED OXYGEN
SENSOR (FRONT)

POWERTRAIN CONTROL
MODULE (PCM)

B-37

MU802665

B-22

Cylinder 1, 4 Heated Oxygen Sensor (front) Circuit

B-21

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-193

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 92) from the output terminal (terminal
No. 4) of the cylinder 1, 4 heated oxygen sensor
(front).

• Terminal No. 2 of the cylinder 1, 4 heated oxygen

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

TECHNICAL DESCRIPTION

• The cylinder 1, 4 heated oxygen sensor (front)

detects the concentration of oxygen in the
exhaust gas; it converts those data to voltage,
and inputs the resulting signals to the PCM.

• When the cylinder 1, 4 heated oxygen sensor

(front) begins to deteriorate, the heated oxygen
sensor signal response becomes poor.

• The PCM forcibly varies the air/fuel mixture to

make it leaner and richer, and checks the
response speed of the cylinder 1, 4 heated oxy-
gen sensor (front). In addition, the PCM also
checks for an open circuit in the cylinder 1, 4
heated oxygen sensor (front) output line.

DESCRIPTIONS OF MONITOR METHODS

Cylinder 1, 4 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

AK303820AB

CONNECTOR: B-37

CYLINDER 1, 4
HEATED OXYGEN
SENSOR (FRONT)

B-37 (GR)

AK303013

CONNECTORS: B-21, B-22

PCM

AIR CLEANER

B-22 (B)

B-21 (B)

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