Mitsubishi Galant 9G. Manual — part 235

MANUAL A/C DIAGNOSIS

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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

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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.

DTC B1021, B1022: Air Thermo Sensor System

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

A/C-ECU

JOINT
CONNECTOR (2)

AIR THERMO
SENSOR

Air Thermo Sensor Circuit

MANUAL A/C DIAGNOSIS

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.

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.

AC305233

C-10 (B)

AY

CONNECTOR: C-10

AC305231

CONNECTOR: C-03, C-126

CC

C-126

C-03

MANUAL A/C DIAGNOSIS

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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. Repair the CAN bus lines

(Refer to GROUP 54C, Diagnosis-Can Bus
Diagnostic Chart

P.54C-607

). 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

Cope with Intermittent Malfunctions

P.00-14

.

NO : Go to Step 3.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827