Mitsubishi Galant 9G. Manual - part 970

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-180

DTC P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control

CAUTION

If DTC P0125 has been set, TCL related DTC 
U1120 is also set. After P0125 has been diag-
nosed, don't forget to erase DTC U1120.

YELLO

W

-GREEN

BLA

CK

AK302836

ENGINE COOLANT
TEMPERATURE SENSOR

POWERTRAIN CONTROL MODULE(PCM)

5 V

93

2

B-104

(MU802406)

69

1

Engine Coolant Temperature Sensor Circuit

1 2

B-21

B-22

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

100

99

92

91

93 94 95

96 97 98

101 102 103 104

105 106 107 108

109 110 111 112 113

AK303036

CONNECTOR: B-104

AB

B-104 (B)

ENGINE
COOLANT
TEMPERATURE
SENSOR

THROTTLE
BODY

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-181

.

CIRCUIT OPERATION

• 5-volt voltage is applied to the engine coolant 

temperature sensor output terminal (terminal No. 
1) from the PCM (terminal No. 93) via the resistor 
in the PCM. The ground terminal (terminal No. 2) 
is grounded with PCM (terminal No. 69).

• The engine coolant temperature sensor is a neg-

ative temperature coefficient type of resistor. It 
has the characteristic that when the engine cool-
ant temperature rises the resistance decreases.

• The engine coolant temperature sensor output 

voltage increases when the resistance increases 
and decreases when the resistance decreases.

.

TECHNICAL DESCRIPTION

• The engine coolant temperature sensor converts 

the engine coolant temperature to a voltage and 
outputs it.

• The PCM checks whether this voltage is within a 

specified range.

.

DESCRIPTIONS OF MONITOR METHODS

• Engine coolant temperature sensor output volt-

age drops from over 40

°C (104°F) to under 40°C 

(104

°F) and keeps under 40°C (104°F) for 5 min-

utes.

• Engine coolant temperature sensor output volt-

age does not reach close loop enable tempera-
ture within specified period when engine coolant 
temperature sensor output voltage at engine start 
is under 7

°C (45°F).

.

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)

• Not applicable

Sensor (The sensor below is determined to be 

normal)

• Mass airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

.

AK303013

CONNECTORS: B-21, B-22

PCM

AB

AIR CLEANER

B-22 (B)

B-21 (B)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-182

DTC SET CONDITIONS <Range/Performance problem - low input (time to reach 
closed loop temperature)>
Logic Flow Chart

.

Check Conditions, Judgement Criteria

• About 60 − 300 seconds have passed for the 

engine coolant temperature to rise to about 7

°C 

(44.6

°F) after starting sequence was completed.

• However, time is not counted when fuel is shut 

off.

.

START

END

YES

NO

NO

YES

MALFUNCTION

GOOD

TIME HAVE PASSED

AFTER STARTING?*

ENGINE
COOLANT
TEMP.

TEMP. WHERE
CLOSED LOOP
STARTS

>

MONITORING

CONDITIONS?

NO

YES

*: SEE DTC SET CONDITIONS-SET CONDITIONS, JUDGMENT CRITERIA

AK302385

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-183

DTC SET CONDITIONS <Range/Performance problem - drift>
Logic Flow Chart

.

Check Conditions, Judgement Criteria

• Engine coolant temperature decreases from 

higher than 40

°C (104°F) to lower than 40°C 

(104

°F).

• Then the engine coolant temperature has contin-

ued to be 40

°C (104°F) or lower for 5 minutes.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13B-6

.

.

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

• Engine coolant temperature sensor failed.

• Harness damage in engine coolant temperature 

sensor circuit or connector damage.

• PCM failed.

START

END

NO

NO

YES

YES

MALFUNCTION

GOOD

UNDER 40˚C (107˚F)

300SECS HAVE PASSED?

NO

YES

OVER 40˚C (107˚F)

YES

OVER 40˚C (107˚F)

NO

AK302387