Mitsubishi Montero (2002-2004). Manual — part 81

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-17

STEP 3. Check air thermo sensor connector D-21 and A/C-
ECU connector D-24 for damage.
Q: Is air thermo sensor connector D-21 and A/C-ECU

connector D-24 in good condition?
YES : Go to Step 4.
NO : Repair or replace the connector. Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Then go

to Step 5.

STEP 4. Check the wiring harness between air thermo
sensor connector D-21 (terminals 1 and 2) and A/C-ECU D-
24 (terminals 30 and 29).
Q: Is the wiring harness between air thermo sensor

connector D-21 (terminals 1 and 2) and A/C-ECU D-24
(terminals 30 and 29) in good condition?
YES : Replace the A/C-ECU. (Refer to

P.55B-136

.) Then go

to Step 5.

NO : Repair the wiring harness. Then go to Step 5.

AC204188

CONNECTORS : D-21, D-24

D-24(B)

D-24(B)

BZ

D-21

D-21

HARNESS SIDE

HARNESS SIDE

22

23

30

31

25

26

33

34

32

24

28

3635

27

29

21

1
2

AC204188

CONNECTORS : D-21, D-24

D-24(B)

D-24(B)

BZ

D-21

D-21

HARNESS SIDE

HARNESS SIDE

22

23

30

31

25

26

33

34

32

24

28

3635

27

29

21

1
2

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-18

STEP 5. Recheck for diagnostic trouble code.
Q: Is DTC 21 or 22 set?

YES : Return to Step 1.
NO : The procedure is complete.

DTC 31: Potentiometer System of Air Mixing Damper Control Motor Assembly

DTC SET CONDITION
DTC 31 is output if there is an open or short circuit in
the potentiometer input circuit, or if there is an open
circuit in the power circuit or earth circuit.

TROUBLESHOOTING HINT

• Malfunction of connector.

• Malfunction of the harness.

• Malfunction of the air mixing damper control

motor and potentiometer.

• Malfunction of the A/C-ECU.

Air Mix Damper Motor Potentiometer Circuit

AC001535 AH

D-20

D-24

CONNECTORS: D-20, D-24

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-19

STEP 1. Using scan tool MB991502, 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 approximately 100% (during

MAX HOT), and approximately 0% (during MAX COOL)?
YES : It can be assumed that this malfunction is

intermittent. (Refer to GROUP 00 - How to Cope with
Intermittent Malfunction

P.00-6

.)

NO : Go to Step 2.

STEP 2. Check the air mixing damper control motor and
potentiometer.

CAUTION

Do not apply battery voltage when the damper is in the
MAX COOL or MAX HOT position.
Check the air mixing damper control motor by the following pro-
cedures.

While checking the air mixing damper control motor, measure
the resistances between terminals numbers 3 and 5 as well as
numbers 3 and 7. At this time, the resistances should change
gradually within the standard value.

Standard value: 1.2

− 4.8 kΩ

Q: Does air mixing damper control motor and

potentiometer work normally?
YES : Go to Step 3.
NO : Replace the air mixing damper control motor and

potentiometer. Then go to Step 5.

LEVER POSITION BATTERY

CONNECTION

LEVER
OPERATION

At the MAX COOL
position

• Connect

terminal 1 to the
positive battery
terminal

• Connect

terminal 2 to the
negative battery
terminal

The lever moves
from the MAX
COOL position to
the outside position

At the MAX HOT
position

• Connect

terminal 2 to the
positive battery
terminal

• Connect

terminal 1 to the
negative battery
terminal

The lever moves
from the MAX HOT
position to the
inside position

ACX01456

MAX HOT
POSITION

MAX COOL
POSITION

AB

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-20

STEP 3. Check air mixing damper control motor and
potentiometer connector D-20 and A/C-ECU connector D-
24 for damage.
Q: Is air mixing damper control motor and potentiometer

connector D-20 and A/C-ECU connector D-24 in good
condition?
YES : Go to Step 4.
NO : Repair or replace the connector. Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Then go

to Step 5.

STEP 4. Check the wiring harness between air mixing
damper control motor and potentiometer connector D-20
(terminals 7, 3 and 5) and A/C-ECU D-24 (terminals 21, 24
and 29).
Q: Is the wiring harness between air mixing damper control

motor and potentiometer connector D-20 (terminals 7, 3
and 5) and A/C-ECU D-24 (terminals 21, 24 and 29) in
good condition?
YES : Replace the A/C-ECU. (Refer to

P.55B-136

.) Then go

to Step 5.

NO : Repair the wiring harness. Then go to Step 5.

AC204188

CONNECTORS : D-20, D-24

D-24(B)

D-24(B)

BY

D-20

D-20

HARNESS SIDE

HARNESS SIDE

22

23

30

31

25

26

33

34

32

24

28

3635

27

29

21

7 6 5 4 3 2 1

AC204188

CONNECTORS : D-20, D-24

D-24(B)

D-24(B)

BY

D-20

D-20

HARNESS SIDE

HARNESS SIDE

22

23

30

31

25

26

33

34

32

24

28

3635

27

29

21

7 6 5 4 3 2 1