Mitsubishi Galant (2004+). Manual — part 734

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-75

DIAGNOSIS

Required Special Tool:

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

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

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A (Vehicles with CAN

communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.

Use scan tool MB991958 to diagnose the CAN bus lines.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to "ON" position.

(3) Diagnose the CAN bus line.
Q: Is the check result satisfactory?

YES : Go to Step 2.
NO : Repair the CAN bus lines. (Refer to GROUP 54C,

Diagnosis-Can Bus Diagnostic Chart

P.54C-621

).

Then go to Step 7.

STEP 2. Recheck for diagnostic trouble code.

Recheck if the DTC is set.

1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.

Q: Is the check result satisfactory?

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

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

− How to

Use Troubleshooting/Inspection Service Points

P.00-6

.

NO : Go to Step 3.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-76

STEP 3. Using scan tool MB991958, check data list item 10:
air mix potentiometer.

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) Connect scan tool MB991958 to the data link connector.
(2) Start the engine.
(3) Set scan tool MB991958 to the data reading mode for item

10: air mix potentiometer.

• Check that the set position of the heater control matches

the displayed position on the scan tool.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor within the specified range?

YES : Replace the A/C-ECU. Then go to Step 7.
NO : Go to Step 4.

STEP 4. Check A/C-ECU connectors C-15, C-16 and air
mixing damper control motor and potentiometer connector
C-105 for loose, corroded or damaged terminals, or
terminals pushed back in the connector.

Q: Are A/C-ECU connectors C-15, C-16 and air mixing

damper control motor and potentiometer connector
C-105 in good condition?
YES : Go to Step 5.
NO : Repair or replace the connector. Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Then go

to Step 7.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305234

C-16 (B)

HARNESS SIDE

C-16

C-15

C-15 (B)

HARNESS SIDE

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

AI

CONNECTORS: C-15, C-16, C-105

C-105

C-105

HARNESS SIDE

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-77

STEP 5. Check the wiring harness between A/C-ECU
connectors C-15 (terminals 16 and 20), C-16 (terminal 29)
and air mixing damper control motor and potentiometer
connector C-105 (terminals 5, 7 and 3).

NOTE: Also check joint connector C-03 for loose, corroded, or
damaged terminals, or terminals pushed back in the connector.
If joint connector C-03 is damaged, repair or replace the con-
nector as described in GROUP 00E, Harness Connector
Inspection

P.00E-2

.

Q: Are the wiring harness between A/C-ECU connectors

C-15 (terminals 16 and 20), C-16 (terminal 29) and air
mixing damper control motor and potentiometer
connector C-105 (terminals 5, 7 and 3) in good
condition?
YES : Go to Step 6.
NO : Repair the wiring harness. Then go to Step 7.

AC305234

C-16 (B)

HARNESS SIDE

C-16

C-15

C-15 (B)

HARNESS SIDE

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

AI

CONNECTORS: C-15, C-16, C-105

C-105

C-105

HARNESS SIDE

AC305231BP

CONNECTOR: C-03

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-78

STEP 6. 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.
(1) Operate the air mixing damper control motor as described

in the table below.

(2) Measure the resistances between connector terminals 3

and 5, and between 3 and 7, while the air mixing damper
control motor is running. The resistances should change
gradually within the standard value.

Standard value: 1.7 (MAX HOT)

− 5.0 (MAX COOL)

k

Ω

Q: Are the air mixing damper control motor and

potentiometer in good condition?
YES : Repair the A/C-ECU. Go to Step 7.
NO : Replace the air mixing damper control motor and

potentiometer. Then go to Step 7 .

LEVER POSITION BATTERY

CONNECTION

LEVER
OPERATION

At the MAX COOL
position

• Connect

terminal 2 to the
positive battery
terminal

• Connect

terminal 1 to the
negative battery
terminal

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

At the MAX HOT
position

• Connect

terminal 1 to the
positive battery
terminal

• Connect

terminal 2 to the
negative battery
terminal

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

AC206296

MAX HOT POSITION

MAX COOL POSITION

1 2

4

3

5

7

6

AB