Mitsubishi Galant (2004+). Manual - part 739

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-95

STEP 3. Using scan tool MB991958, check actuator test 
item 13, 14, 15, 16, 17: Air outlet c/o dumper.

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) Use scan tool MB991958 to run the actuator test.

Item 13: air mix damper motor (FACE position)
Item 14: air mix damper motor (FOOT/FACE position)
Item 15: air mix damper motor (FOOT position)
Item 16: air mix damper motor (DEF/FOOT position)
Item 17: air mix damper motor (DEF position)

• Check that the mode selection damper control motor 

operates.

(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 connector C-15 and mode 
selection damper control motor and potentiometer 
connector C-102 for loose, corroded or damaged 
terminals, or terminals pushed back in the connector.

Q: Are A/C-ECU connector C-15 and mode selection 

damper control motor and potentiometer connector 
C-102 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

AC305233

CONNECTOR: C-15

BG

C-105 (B)

HARNESS SIDE

AC305231

C-102

HARNESS SIDE

CD

CONNECTOR: C-102

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-96

STEP 5. Check the wiring harness between A/C-ECU 
connector C-15 (terminals 11 and 4) and mode selection 
damper control motor and potentiometer connector C-102 
(terminals 1 and 2).

Q: Are the wiring harnesses between A/C-ECU connector 

C-15 (terminals 11 and 4) and mode selection damper 
control motor and potentiometer connector C-102 
(terminals 1 and 2) in good condition?
YES : Go to Step 6.
NO :  Repair the wiring harness. Then go to Step 7.

AC305233

CONNECTOR: C-15

BG

C-105 (B)

HARNESS SIDE

AC305231

C-102

HARNESS SIDE

CD

CONNECTOR: C-102

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-97

STEP 6. Check the mode selection damper control motor.

CAUTION

Do not apply battery voltage when the damper is in the 
FACE or DEF position.
Check the mode selection damper control motor by the follow-
ing procedures.

Q: Is the mode selection damper control motor in good 

condition?
YES : Go to Step 7.
NO :  Replace the mode selection damper control motor 

and potentiometer. Then go to Step 7.

LEVER POSITION BATTERY 

CONNECTION

LEVER 
OPERATION

At the FACE 
position

• Connect 

terminal 2 to the 
positive battery 
terminal

• Connect 

terminal 1 to the 
negative battery 
terminal

The lever moves 
from the FACE 
position to the DEF 
position

At the DEF position

• Connect 

terminal 1 to the 
positive battery 
terminal

• Connect 

terminal 2 to the 
negative battery 
terminal

The lever moves 
from the DEF 
position to the 
FACE position

AC209789

FACE POSITION

DEF POSITION

AB

1 2

4

3

5

7

6

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-98

STEP 7. Recheck for diagnostic trouble code.

Check again if the DTC is set.

1. Connect scan tool MB991958 to the data link connector
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : Repair the A/C-ECU. The procedure is complete.
NO :  Return to Step 1.

DTC U1073: Bus Off

CAUTION

If DTC U1073 is set in the A/C-ECU, diagnose the 
CAN main bus line.

CAUTION

Whenever the ECU is replaced, ensure that the 
communication circuit is normal.

.

TROUBLE JUDGMENT
DTC U1073 will be stored when the A/C-ECU ceases 
CAN communication (bus off) and then resumes the 
communication when the ignition switch is turned to 
the "LOCK" (OFF) position.

.

TECHNICAL DESCRIPTION (COMMENT) 
The wiring harness wire or connectors may have 
loose, corroded, or damage terminals, or terminals 
pushed back in the connector, or the A/C-ECU may 
be defective.

.

TROUBLESHOOTING HINTS

• Defective connector(s) or wiring harness

• Malfunction of the A/C-ECU

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)

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827