Mitsubishi Montero (2002-2004). Manual — part 591

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-61

.

CIRCUIT OPERATION

• 5-volt voltage is applied to the engine coolant

temperature sensor output terminal (terminal No.
1) from the PCM (terminal No. 98) via the resistor
in the PCM. The ground terminal (terminal No. 2)
is grounded with (terminal No. 96).

• 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 resistor decreases.

• The engine coolant temperature sensor output

voltage increases when the resistor increases
and decreases when the resistor decreases.

.

TECHNICAL DESCRIPTION

• The engine coolant temperature sensor converts

the engine coolant temperature to a voltage and
output it.

• The PCM checks whether this voltage is within a

specified range.

.

DTC SET CONDITIONS

Check Conditions

• Engine coolant temperature was 7°C (45°F) or

more immediately before the engine was stopped
at the last drive.

• Engine coolant temperature was 7°C (45°F) or

more when the engine started.

Judgement Criteria

• Engine coolant temperature fluctuates within 1°C

(1.8

°F) after 5 minutes have passed since the

engine was started.

• However, time is not counted if any of the follow-

ing conditions are met.

1. Intake air temperature is 60

°C (140°F) or

more.

2. Volume airflow sensor output frequency is 70

Hz or less.

3. During fuel shut-off operation.

• The PCM monitors for this condition once during

the drive cycle.

.

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

• Engine coolant temperature sensor failed.

• Open or shorted engine coolant temperature sen-

sor circuit, or loose connector.

• PCM failed.

AK200942

ENGINE COOLANT
TEMPERATURE SENSOR

AK200942AB

B-37(B)

CONNECTOR: B-37

AK201038AF

CONNECTOR: D-135

PCM

D-135(GR)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

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DIAGNOSIS

Required Special Tool:

• MB991502: Scan Tool (MUT-II)

STEP 1. Using scan tool MB991502, check data list item 21:
Engine Coolant Temperature Sensor.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool MB991502 to the data reading mode for item

21, Engine Coolant Temperature Sensor.

• The engine coolant temperature and temperature

shown with the scan tool should approximately match.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent.

Refer to GROUP 00, How to Use Troubleshooting/
Inspection Service Points

P.00-6

.

NO : Go to Step 2.

ACX01539

16-PIN

MB991502

AC

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-63

STEP 2. Check the sensor output voltage at engine coolant
temperature sensor connector B-37 by backprobing.
(1) Do not disconnect the connector B-37.
(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal No. 1 and ground by

backprobing.

• When engine coolant temperature is −20°C (−4°F), volt-

age should be 3.9 and 4.5 volts.

• When engine coolant temperature is 0°C (32°F), voltage

should be 3.2 and 3.8 volts.

• When engine coolant temperature is 20°C (68°F), volt-

age should be 2.3 and 2.9 volts.

• When engine coolant temperature is 40°C (104°F), volt-

age should be 1.3 and 1.9 volts.

• When engine coolant temperature is 60°C (140°F), volt-

age should be 0.7 and 1.3 volts.

• When engine coolant temperature is 80°C (176°F), volt-

age should be 0.3 and 0.9 volt.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?

YES : Go to Step 3.
NO : Go to Step 5.

STEP 3. Check connector B-37 at the engine coolant
temperature sensor for damage.
Q: Is the connector in good condition?

YES : Go to Step 4.
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)

AK201572

2

1

AB

B-37 HARNESS
CONNECTOR:
HARNESS SIDE

AK200943

1

2

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-37

B-37(B)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-64

STEP 4. Using scan tool MB991502, check data list item 21:
Engine Coolant Temperature Sensor.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool MB991502 to the data reading mode for item

21, Engine Coolant Temperature Sensor.

• The engine coolant temperature and temperature

shown with the scan tool should approximately match.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent.

Refer to GROUP 00, How to Use Troubleshooting/
Inspection Service Points

P.00-6

.

NO : Replace the PCM. Then go to Step 14.

STEP 5. Check connector B-37 at engine coolant
temperature sensor for damage.
Q: Is the connector in good condition?

YES : Go to Step 6.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then go to Step 14.

ACX01539

16-PIN

MB991502

AC

AK200943

1

2

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-37

B-37(B)