Mitsubishi Galant (2004+). Manual - part 731

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-63

STEP 3. Using scan tool MB991958, check data list item 02: 
Ambient air 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 

02: Ambient air temperature sensor.

• Check that the ambient temperature matches the dis-

played value on the scan tool.

NOTE: When this DTC is set and the system is fail-safe sta-
tus, the value of service data displays 20

°

C.

(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 8.
NO :  Go to Step 4.

STEP 4. Check ambient air temperature sensor connector 
A-25 for loose, corroded or damaged terminals, or 
terminals pushed back in the connector.

Q: Is ambient air temperature sensor connector A-25 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 8.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305210

A-25 (BR)

HARNESS SIDE

CONNECTOR: A-25

AP

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-64

STEP 5. Check the ambient air temperature sensor.

(1) Disconnect ambient air temperature sensor connector A-25.

CAUTION

The ambient air temperature sensor should be checked 
without removing it. If the sensor is removed, it is no 
longer serviceable.

(2) Measure the resistance between the sensor terminals 

under at least two temperatures. The resistance values 
should meet the values shown.
NOTE: The temperature should be within the shown range.

Q: Is the ambient air temperature sensor in good 

condition?
YES : Go to Step 6.
NO :  Replace the ambient air temperature sensor. Then go 

to Step 8.

STEP 6. Check A/C-ECU connectors C-15 and C-16 for 
loose, corroded or damaged terminals, or terminals 
pushed back in the connector.

Q: Are A/C-ECU connectors C-15 and C-16 in good 

condition?
YES : Go to Step 7.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Then go 

to Step 8.

AC305210

A-25 (BR)

HARNESS SIDE

CONNECTOR: A-25

AP

AC209942AB

REGISTANCE 
k

Ω

10

20

30

40

0

0

20

(32) (68)

TEMPERATURE ˚C (˚F)

40

(104)

60

(140)

-20

(-4)

-30

(-22)

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

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-65

STEP 7. Check the wiring harness between A/C-ECU 
connector C-15 (terminal 20), C-16 (terminal 23) and 
ambient air temperature sensor connector A-25 (terminals 
1 and 2).

NOTE: Also check intermediate connector C-23 and joint con-
nector C-03 for loose, corroded, or damaged terminals, or ter-
minals pushed back in the connector. If intermediate connector 
C-23 or joint connector C-03 is damaged, repair or replace the 
connector as described in GROUP 00E, Harness Connector 
Inspection 

P.00E-2

.

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

C-15 (terminal 20), C-16 (terminal 23) and ambient air 
temperature sensor connector A-25 (terminals 1 and 2) 
in good condition?
YES : Replace the A/C-ECU. Then go to Step 8.
NO :  Repair the wiring harness. Then go to Step 8.

AC305210

A-25 (BR)

HARNESS SIDE

CONNECTOR: A-25

AP

AC305234

HARNESS SIDE

C-16

C-15

HARNESS SIDE

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

C-15 (B)

C-16 (B)

CONNECTORS: C-15, C-16,C-23

C-23

C-23

AH

AC305231BP

CONNECTOR: C-03

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-66

STEP 8. 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 : The procedure is complete.
NO :  Return to Step 1.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827