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
NO
NO
YES
MALFUNCTION
GOOD
TIME HAVE PASSED
AFTER STARTING?*
ENGINE COOLANT TEMP.
>=77˚C (171˚F)
*: See DTC SET CONDITIONS-JUDGMENT CRITERIA
MONITORING
CONDITIONS?
NO
YES
AK204044
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-191
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
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-192
DIAGNOSIS
STEP 1. Check the cooling system.
Refer to GROUP 14, Engine Cooling Diagnosis
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
99
92
91
93 94 95
96 97 98
101 102 103 104
105 106 107 108
109 110 111 112 113
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
AK303819
1
2
3
4
BLA
CK
BLUE
BLA
CK
TO PCM
FROM MFI RELAY
PINK
69
92
4
3
1
CYLINDER 1, 4
HEATED OXYGEN
SENSOR (FRONT)
POWERTRAIN CONTROL
MODULE (PCM)
B-37
MU802665
2
B-22
Cylinder 1, 4 Heated Oxygen Sensor (front) Circuit
B-21
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
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
AB
AIR CLEANER
B-22 (B)
B-21 (B)
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