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

TSB Revision

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

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CONNECTOR: D-135

HARNESS CONNECTOR: 
COMPONENT SIDE

AB

PCM

D-135(GR)

TSB Revision

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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CONNECTOR: D-135

HARNESS CONNECTOR: 
COMPONENT SIDE

AB

PCM

D-135(GR)

TSB Revision

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

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119

120

CONNECTOR: D-135

HARNESS CONNECTOR: 
COMPONENT SIDE

AB

PCM

D-135(GR)

TSB Revision

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.