Mitsubishi Galant (2004+). Manual - part 791

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-9

DIAGNOSTIC TROUBLE CODE PROCEDURES

DTC B1001, B1002: Interior Temperature Sensor System

DTC SET CONDITION

• DTC B1001 is set if there is a short circuit in the 

interior temperature sensor input circuit.

• DTC B1002 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 interior air temperature sensor, 

or connector(s) or wiring between the two may be 
defective.

Past trouble

• If DTC B1001 or B1002 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 interior air temperature sensor. If the con-
nectors 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.

.

A/C-ECU

JOINT
CONNECTOR (2)

INTERIOR
TEMPERATURE
SENSOR

Interior Temperature Sensor Circuit

AC305233

C-16 (B)

C-15 (B)

CONNECTORS: C-15, C-16

BE

AC305231CL

CONNECTOR: C-03, C-123

C-123

C-03

AUTO A/C DIAGNOSIS

TSB Revision

AUTOMATIC AIR CONDITIONING

55B-10

TROUBLESHOOTING HINT

• Malfunction of connector.

• Malfunction of the harness.

• Malfunction of the interior temperature sensor.

• 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)

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-621

). 

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 

Use Troubleshooting/Inspection Service Points 

P.00-6

.

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