Mitsubishi Galant (2004+). Manual - part 728

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-51

STEP 5. Recheck for diagnostic trouble code.

Check again if the DTC is set.

1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES : A poor connection, open circuit or other intermittent

malfunction is present in the lines between the
powertrain control module and the A/C-ECU (Refer to
GROUP 00E, Harness Connector Inspection

P.00E-2

NO : Replace the A/C-ECU. On completion, check that the

DTC is not reset.

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-52

DTC U1111: Multi-Center Display Unit (Middle Grade Type) Time-out

CAUTION

If DTC U1111 is set in the A/C-ECU, diagnose the
CAN main bus line.

CAUTION

Whenever the ECU is replaced, ensure that the
communication circuit is normal.

TROUBLE JUDGMENT
The A/C-ECU receives signals from the multi-center
display unit (middle grade type). If the ECU cannot
receive the signal related to the multi-center display
unit, DTC U1111 will be set.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

• Connector(s) or wiring harness in the CAN bus

lines between the A/C-ECU and the middle-grade
multi-center display unit, the power supply sys-
tem to the display unit, the display unit itself, or
the A/C-ECU may be defective.

Past trouble

• When DTC U1111 is set as a past trouble, carry

out diagnosis with particular emphasis on con-
nector(s) or wiring harness in the CAN bus lines
between the A/C-ECU and the middle-grade
multi-center display unit, the power supply sys-

tem to the display unit. If the connectors and wir-
ing are normal, and obviously the ECU or the
middle-grade multi-center display is the cause of
the trouble, replace the ECU or the middle-grade
multi-center display. If in doubt, do not replace
the ECU or the display unit.
NOTE: For a past trouble, you cannot find it by
the scan tool CAN bus diagnostics even if there is
a failure in the CAN bus lines. In this case, refer
to GROUP 00, How to Cope with Intermittent
Malfunctions

P.00-6

.) and check the CAN bus

lines. You can narrow down the possible cause of
the trouble by referring to the DTC, which is set
regarding the CAN communication-linked ECUs
(Refer to GROUP 54C

−

Explanation about the

scan tool CAN bus diagnostics

P.54C-6

TROUBLESHOOTING HINTS

• Malfunction of middle-grade multi-center display

unit

• Malfunction of the A/C-ECU

• Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:

• 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)

MANUAL A/C DIAGNOSIS

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STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.

CAUTION

To prevent damage to scan tool (MUT-III), always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool (MUT-III).
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?

YES : Go to Step 2.
NO : Repair the CAN bus line (Refer to GROUP 54C,

Diagnosis

P.54C-14

STEP 2. Using scan tool MB991958, read the powertrain
control module diagnostic trouble code.

Check that the middle-grade multi-center display unit sets a
DTC.
(1) Turn the ignition switch to the "ON" position.
(2) Check for the DTC related to the middle-grade multi-center

display unit.

(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?

YES : Refer to GROUP 54A, Middle-grade multi-center

display unit

− Diagnosis

P.54A-237

NO : Go to Step 3.

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-54

STEP 3. Using scan tool MB991958, check for any
diagnostic trouble code.

Check if a DTC, which relates to CAN communication-linked
systems below, is set.

• ETACS-ECU

DTC indicating a time-out error of middle-grade multi-center
display unit

(1) Turn the ignition switch to the "ON" position.
(2) Check for a DTC related to the relevant system.

(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?

YES : Go to Step 4.
NO : Go to Step 5.

STEP 4. Recheck for diagnostic trouble code.

Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.

(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?

YES : Replace the middle-grade multi-center display unit.

On completion, check that the DTC is not reset.

NO : A poor connection, open circuit or other intermittent

malfunction is present in the CAN bus lines between
the middle-grade multi-center display unit and the
A/C-ECU (Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points

P.00-6

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

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