Mitsubishi Galant 9G. Manual — part 234

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-12

.

DTC SET CONDITION

• DTC B1011 is set if there is a short circuit in the

ambient air temperature sensor input circuit.

• DTC B1012 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 ambient air temperature sen-

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

Past trouble

• If DTC B1011 or B1012 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 ambient air temperature 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 ambient air temperature sen-

sor.

• Malfunction of the A/C-ECU.

AC305233AX

CONNECTORS: C-10, C-23

C-10 (B)

C-23

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 8.

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

MANUAL A/C DIAGNOSIS

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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

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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)