Mitsubishi Montero (2004+). Manual — part 641

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-53

STEP 29. Check the A/C switch.

There should be continuity between terminals 10 and 13 while
the A/C switch is pushed.
Q: Is the check result normal?

YES : Replace the A/C-ECU (Refer to

P.55B-142

). Then go

to Step 30.

NO : Replace the automatic air-conditioning control panel.

Check that the air conditioning works normally.

STEP 30. Retest the system.
Q: Do the air conditioning work normally?

YES : No action is necessary and testing is complete.
NO : Replace the powertrain control module. Check that

the air conditioning works normally.

AC205403

18

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10

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2

1

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AF

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-54

INSPECTION PROCEDURE 3: A/C Outlet Air Temperature cannot be Set.

.

TECHNICAL DESCRIPTION (COMMENT)
If the A/C outlet air temperature can not be adjusted,
the air mixing damper control motor system may be
defective.

.

TROUBLESHOOTING HINTS

• Malformation of the photo sensor

• Malformation of the air mixing damper control

motor and potentiometer

• Malformation of the A/C-ECU

• Malformation of the flexible flat cable

Photo Sensor and Air Mix Damper Motor Circuit

AC204170 DZ

D-23(B)

D-24(B)

D-20

D-09

CONNECTORS : D-09, D-20, D-23, D-24

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-55

DIAGNOSIS

Required Special Tools:

• MB991223: Harness Set

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B (Vehicles without

CAN communication system)

STEP 1. Using scan tool MB991958, read the diagnostic
trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOOK (OFF)" position.
Q: Is a diagnostic trouble code set?

YES : Refer to

P.55B-7

.

NO : Go to Step 2.

STEP 2. Using scan tool MB991958, check data list item 11:
Inside air temperature sensor.

Check the data list.
Item 11: Inside air temperature sensor
Q: Are the inside air temperature and indicated

temperature on scan tool MB991958 almost equal?
YES : Go to Step 3.
NO : Replace the A/C-ECU (Refer to

P.55B-142

). The

temperature control should work normally.

STEP 3. Using scan tool MB991958, check data list item 13:
Outside air temperature sensor.
Check the data list.
Item 13: Outside air temperature sensor
Q: Are the outside air temperature and indicated

temperature on scan tool MB991958 almost equal?
YES : Go to Step 4.
NO : Check the outside air temperature sensor system

(Refer to

P.55B-9

).

AC307591 AB

MB991911

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-56

STEP 4. Using scan tool MB991958, check data list item 15:
Heater water temperature sensor.

Check the data list.
Item 15: Heater water temperature sensor
Q: Are the heater core surface temperature and indicated

temperature on scan tool MB991958 almost equal?
YES : Go to Step 5.
NO : Check the heater water temperature sensor system

(Refer to

P.55B-13

).

STEP 5. Using scan tool MB991958, check data list item 21:
Air thermo sensor.

Check the data list.
Item 21: Air thermo sensor
Q: Are the evaporator blowout temperature and indicated

temperature on scan tool MB991958 almost equal?
YES : Go to Step 6.
NO : Check the outside air temperature sensor system

(Refer to

P.55B-9

).

STEP 6. Using scan tool MB991958, check data list item 31:
Air mix damper potentiometer.

Check the data list.
Item 31: Air mix damper potentiometer
Q: Does the data list show 100% (at MAX HOT) or 0% (at

MAX COOL)?
YES : Go to Step 7.
NO : Check the air mixing damper potentiometer system

(Refer to

P.55B-20

)

STEP 7. Check the photo sensor.

The blower speed should drop when the light-sensing section
of the photo sensor is covered with your hand.
Q: Is the check result normal?

YES : Go to Step 10.
NO : Go to Step 8.

ACX01825AE

PHOTO
SENSOR

DEFROSTER
NOZLE