Mitsubishi Galant (2004+). Manual - part 793

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-17

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 12: When Sunlight Intensity Changes, Air Outlet Temperature Does Not 
Change.

.

CIRCUIT OPERATION
When the blower air temperature cannot be changed 
even if the preset temperature is changed, the sen-
sors may be defective.

.

TROUBLESHOOTING HINTS

• Improper amount of refrigerant

• Malfunction of the A/C pressure sensor

• Malfunction of the photo sensor

• Malfunction of the A/C-ECU

• The wiring harness or connectors may have 

loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector

DIAGNOSIS

Required Special Tools:

•  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)

A/C-ECU

PHOTO
SENSOR

Photo Sensor Motor Circuit

AC305231

C-04

CP

CONNECTORS: C-04

AC305233

C-16 (B)

C-15 (B)

CONNECTORS: C-15, C-16

BE

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-18

STEP 1. Check the defogger and outside/inside air 
selection damper control motor operation.
Q: Do the defogger and outside/inside air selection damper 

control motor work normally?
YES : Go to Step 2.
NO :  Refer to GROUP 55A, Manual A/C Diagnosis, 

P.55A-181

.

STEP 2. Using scan tool MB991958, read 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.
Check if an A/C-ECU 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 DTC set?

YES : Refer to 

P.55B-8

.

NO :  Go to Step 3.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-19

STEP 3. Using scan tool MB991958, check data list item 06: 
Photo sensor.

(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 

06: Photo sensor.

• Check that the display on the scan tool changes when 

the photo sensor is covered with hands.

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

YES : Go to Step 7.
NO :  Go to Step 4.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-20

STEP 4. Check A/C-ECU connectors C-15, C-16 and photo 
sensor connector C-04 for loose, corroded or damaged 
terminals, or terminals pushed back in the connector.

Q:  Are A/C-ECU connectors C-15, C-16 and photo sensor 

connector C-04 in good condition?
YES : Go to Step 5.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Check 

that the air conditioning works normally.

AC305231

CONNECTOR: C-04

CM

HARNESS SIDE

AC305234

CONNECTORS: C-15, C-16

C-16 (B)

HARNESS SIDE

C-16

C-15

C-15 (B)

HARNESS SIDE

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AG