Mitsubishi 380. Manual - part 230

ENGINE COOLING DIAGNOSIS

ENGINE COOLING

14-4

INSPECTION PROCEDURE 2: Engine Overheating

DIAGNOSIS

STEP 1. Remove the radiator cap and check for coolant 
contamination.

Q: Is the coolant contaminated with rust and oil?

YES : Replace it. Refer to

 P.14-27

.

NO :  There is no action to be taken. Go to Step 2.

STEP 2. Check the radiator cap valve opening pressure.

NOTE:  Be sure that the cap is clean before testing. Rust or 
other foreign material on the cap seal will cause an improper 
reading.
(1) Use a cap adapter to attach the cap to the tester.
(2) Increase the pressure until the gauge indicator stops 

moving.

Minimum limit: 83 kPa (12 psi)
Standard value: 93 

− 123 kPa (14 − 18 psi)

Q: Does the reading remain at or above the minimum limit?

YES : Go to Step 3.
NO :  Replace the radiator cap. Then go to Step 5.

STEP 3. Check thermostat operation.
Refer to 38.

Q: Does the thermostat operate correctly?

YES : Go to Step 4.
NO :  Replace the thermostat, then go to Step 5.

STEP 4. Check the drive belt for slippage or damage.
Refer to GROUP 00, Maintenance Service 

− Drive Belts 

(Check Condition). <3.8L Engine>39 .

Q: Is the drive belt loose or damaged?

YES : Adjust or replace the drive belt, then go to Step 5.
NO :  There is no action to be taken.

STEP 5. Retest the system.
Check the engine coolant temperature.

Q: Is the engine coolant temperature abnormally high?

YES : Return to Step 2.
NO :  The procedure is complete.

ACX01845 AB

CAP ADAPTER

ENGINE COOLING DIAGNOSIS

ENGINE COOLING

14-5

INSPECTION PROCEDURE 3: Radiator Fan and Condenser Fan do not Operate

.

CIRCUIT OPERATION

• The fan controller is powered from fusible link 

No.2.

• The engine-ECU uses input signals from the A/C 

switch, the water temperature sensor unit and the 
vehicle speed sensor <M/T> or the output shaft 
speed sensor <A/T> to control the speed of the 
radiator fan motor and the condenser fan motor.

• The engine-ECU controls the fan controller to 

activate the radiator fan motor and the condenser 
fan motor.

.

TECHNICAL DESCRIPTION

• The cause could be a malfunction of the fan con-

troller power supply or earth circuit.

• If the communication line wiring harness between 

the fan controller and the engine-ECU is 
short-circuited to earth, the radiator fan motor 
and the condenser fan motor will not rotate.

• The cause could also be a malfunction of input 

signal from the A/C switch, the water temperature 
sensor unit and the vehicle speed sensor <M/T> 
or the output shaft speed sensor <A/T> to the 
engine-ECU.

• The cause could also be a malfunction of the fan 

controller or the engine-ECU.
 

.

TROUBLESHOOTING HINTS

• Malfunction of fusible link No.2

• Malfunction of fan control relay

• Malfunction of cooling fan motor and fan control-

ler

• Malfunction of engine-ECU.

• Damaged wiring harness or connector

• Refer to component locations GROUP-1

• Refer to configuration diagrams GROUP-1

• Refer to circuit diagrams GROUP-1

ENGINE COOLING DIAGNOSIS

ENGINE COOLING

14-6

DIAGNOSIS

STEP 1. Measure the power supply voltage at fan 
controller connector A-24.

(1) Disconnect fan controller connector A-24 and measure 

wiring harness side connector.

(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between fan controller connector A-24 

terminal 3 and body earth.

• The voltage should measure system voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Connect fan controller connector A-24.

Q: Is the measured voltage system voltage?

YES : Go to Step 17.
NO :  Go to Step 2.

STEP 2. Check the fan controller connector A-24.

Q: Is the connector in good condition?

YES : Go to Step 3.
NO :  Repair or replace the connector. Then go to Step 24.

04DB008A

1

2

3

A-24

Connector: A-24

3 2 1

04DB009A

Connector A-24

(Component side)

04DB008A

1

2

3

A-24

Connector: A-24

ENGINE COOLING DIAGNOSIS

ENGINE COOLING

14-7

STEP 3. Check the fusible link No.2.

Q: Is the fusible link No.2 in good condition?

YES : Go to Step 4.
NO :  Replace the fusible link No.2. Then go to Step 24.

STEP 4. Measure the power supply voltage at fan control 
relay connector A-10X.

(1) Disconnect fan control relay connector A-10X (remove the 

fan control relay) and measure relay box side connector.

(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between fan control relay connector 

A-10X terminal 4 and body earth.

• The voltage should measure system voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Connect fan control relay connector A-10X (install the fan 

control relay).

Q: Is the measured voltage system voltage?

YES : Go to Step 7.
NO :  Go to Step 5.

04DB010A

Fusible link

No.2

Relay box

Fan control

relay

04DB012A

Fusible link

No.2

Relay box

Fan control

relay

A-10X

4

04DB013A

A-10X Connector

(Relay box side)