Mitsubishi Galant 9G. Manual — part 306

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-10

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-607

).

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

Cope with Intermittent Malfunctions

P.00-14

.

NO : Go to Step 3.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

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AUTOMATIC AIR CONDITIONING

55B-11

STEP 3. Using scan tool MB991958, check data list item 01:
interior temperature sensor.

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

01: Interior temperature sensor.

• Check that the interior temperature matches the dis-

played value on the scan tool.

NOTE: When this DTC is set and the system is in fail-safe
status, the value of service data displays 25

°

C.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Does the interior temperature match the displayed value

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

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

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AUTOMATIC AIR CONDITIONING

55B-12

STEP 4. Check A/C-ECU connector C-15, C-16 and interior
temperature sensor connector C-123 for loose, corroded
or damaged terminals, or terminals pushed back in the
connector.
Q: Are A/C-ECU connectors C-15, C-16 and interior

temperature sensor connector C-123 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.

AC305234

CONNECTORS: C-15, C-16

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

AG

AC305231CK

CONNECTOR: C-123

HARNESS SIDE

AUTO A/C DIAGNOSIS

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AUTOMATIC AIR CONDITIONING

55B-13

STEP 5. Check the wiring harness between A/C-ECU
connector C-15 (terminals 20), C-16 (terminals 22) and
interior temperature sensor connector C-123 (terminals 1
and 2).

AC305234

CONNECTORS: C-15, C-16

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

AG

AC305232

CONNECTORS: C-03, C-123

AQ

C-03

C-123

JUNCTION BLOCK SIDE

C-03

HARNESS SIDE

C-123