Mitsubishi Galant (2004+). Manual - part 719

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-15

STEP 5. Check the ambient air temperature sensor.

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

(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 connector C-10 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.

Q: Is A/C-ECU connector C-10 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)

AC305233AW

CONNECTOR: C-10

HARNESS SIDE

C-10 (B)

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-16

STEP 7. Check the wiring harness between A/C-ECU 
connector C-10 (terminals 10 and 14) 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-10 (terminals 10 and 14) 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.

AC305234

C-23

C-10

C-23

HARNESS SIDE

CONNECTORS: C-10,C-23

AD

C-10 (B)

AC305210

A-25 (BR)

HARNESS SIDE

CONNECTOR: A-25

AP

AC305231BP

CONNECTOR: C-03

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-17

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

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-18

DTC B1021, B1022: Air Thermo Sensor System

.

DTC SET CONDITION

• DTC B1021 is set if there is a short circuit in the 

air thermo sensor input circuit.

• DTC B1022 is set if there is a defective connector 

connection, or if there is an open circuit in the 
harness.

.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

• The A/C-ECU, the air thermo sensor, or connec-

tor(s) or wiring between the two may be defec-
tive.

Past trouble

• If DTC B1021 or B1022 is stored as a past trou-

ble, carry out diagnosis with particular emphasis 
on wiring and connector(s) between the A/C-ECU 
and the air thermo sensor. If the connectors and 
wiring are normal, and obviously the ECU is the 
cause of the trouble, replace the ECU. If in doubt, 
do not replace the ECU.

TROUBLESHOOTING HINT

• Malfunction of connector.

• Malfunction of the harness.

• Malfunction of the air thermo sensor.

• Malfunction of the A/C-ECU.

A/C-ECU

JOINT
CONNECTOR (2)

AIR THERMO
SENSOR

Air Thermo Sensor Circuit

AC305233

C-10 (B)

AY

CONNECTOR: C-10

AC305231

CONNECTOR: C-03, C-126

CC

C-126

C-03