Mitsubishi Montero (2002-2004). Manual — part 601

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-101

STEP 10. Check for harness damage between engine
coolant temperature sensor connector B-37 (terminal No.
2) and PCM connector D-135 (terminal No. 96).
Q: Is the harness wire in good condition?

YES : Replace the PCM. Then go to Step 14.
NO : Repair it. Then go to Step 14.

AK200943

1

2

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-37

B-37(B)

AK200947

91

92

93

94

95

96

97

98

99

100

101

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104

105

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111

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CONNECTOR: D-135

HARNESS CONNECTOR:
COMPONENT SIDE

AB

PCM

D-135(GR)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-102

STEP 11. Check the engine coolant temperature sensor.
(1) Disconnect the engine coolant temperature sensor

connector B-37.

(2) Remove the engine coolant temperature sensor.

(3) With the temperature sensing portion of engine coolant

temperature sensor immersed in hot water, check
resistance.

Standard value:

14

− 17 kiloohms [at −20°C (−4°F)]

5.1

− 6.5 kiloohms [at 0°C (32°F)]

2.1

− 2.7 kiloohms [at 20°C (68°F)]

0.9

− 1.3 kiloohms [at 40°C (104°F)]

0.48

− 0.68 kiloohm [at 60°C (140°F)]

0.26

− 0.36 kiloohm [at 80°C (176°F)]

(4) Apply 3M

ä AAD part number 8731 or equivalent on the

screw section of the engine coolant temperature sensor.

(5) Install the engine coolant temperature sensor, and tighten

to the specified torque.

Tightening torque: 29

± 10 N⋅m (22 ± 7 ft-lb)

Q: Is the resistance at the standard value?

YES : Go to Step 12.
NO : Replace the engine coolant temperature sensor. Then

go to Step 14.

STEP 12. Check connector D-135 at PCM for damage.
Q: Is the connector in good condition?

YES : Go to Step 13.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then go to Step 14.

AK200943

1

2

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-37

B-37(B)

AKX01622

AKX01623 AB

AK200947

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92

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120

CONNECTOR: D-135

HARNESS CONNECTOR:
COMPONENT SIDE

AB

PCM

D-135(GR)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-103

STEP 13. Check for harness damage between engine
coolant temperature sensor connector B-37 (terminal No.
1) and PCM connector D-135 (terminal No. 98).
Q: Is the harness wire in good condition?

YES : Replace the PCM. Then go to Step 14.
NO : Repair it. Then go to Step 14.

STEP 14. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to

GROUP 13A, Procedure 6

− Other Monitor

P.13Ab-2

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0125 set?

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

AK200943

1

2

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-37

B-37(B)

AK200947

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

CONNECTOR: D-135

HARNESS CONNECTOR:
COMPONENT SIDE

AB

PCM

D-135(GR)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-104

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.

.

DTC SET CONDITIONS

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 volume airflow sensors output frequency is in

the low frequency state for 300 seconds or less.

Judgment Criteria

• The time for the engine coolant temperature to

rise to 77

°C (171°F) takes longer than approxi-

mately 13 to 20 minutes.

• The PCM monitors for this condition once during

the drive cycle.

.

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

• The thermostat is faulty.

• PCM failed.

DIAGNOSIS

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

P.14-2

.

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.