2005 MITSUBISHI 380 heater

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-63
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 : Replace the A/C-ECU. 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 multi-center display unit and the A/C-ECU (Refer
to GROUP 00, How to Use
Troubleshooting/Inspection Service Points
How to
Cope with Intermittent Malfunctions P.00-14).

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-64
DTC U1120: Failure Information on Electronic control unit (Related to Engine)
If DTC U1120 is set in the A/C-ECU, diagnose the
CAN main bus line.
Whenever the ECU is replaced, ensure that the
communication circuit is normal.
The engine control system- related DTC may be
set when DTC U1120 is set. (For details refer to
GROUP 00, Intersystem Affiliated DTC Reference
Ta b l e P.00-17.) Diagnose the engine control sys-
tem first when the engine control system- related
DTC is set.
.
TROUBLE JUDGMENT
The A/C-ECU receives engine control sys-
tem-related signal from the Electronic control unit by
the CAN bus lines. If a fail-safe related data is con-
tained in the signal from the Electronic control unit,
DTC U1120 will be stored.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
The wiring harness wire or connectors may have
loose, corroded, or damage terminals, or termi-
nals pushed back in the connector, the Electronic
control unit, or the A/C-ECU may be defective.Past trouble
If DTC U1120 is stored as a past trouble, carry
out diagnosis with particular emphasis on wiring
and connector(s) in the CAN bus line between
the A/C-ECU and the Electronic control unit, and
the power supply system to the Electronic control
unit. 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.
NOTE: For a past trouble, you cannot find it by
the diagnostic tool CAN bus diagnostics even if
there is a failure in CAN bus lines. In this case,
refer to GROUP 00, How to Use Troubleshoot-
ing/Inspection Service Points
How to Cope with
Intermittent Malfunctions P.00-14.) and check the
CAN bus lines. You can narrow down the possi-
ble cause of the trouble by referring to the DTC,
which is set regarding the CAN communica-
tion-linked ECUs (Refer to GROUP 54C
Expla-
nation about the diagnostic tool CAN bus
diagnostics P.54C-6).
.
TROUBLESHOOTING HINTS
Malfunction of the A/C-ECU.
Malfunction of the Electronic control unit.
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
DIAGNOSIS
Required Special Tool:
: Diagnostic 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)

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-65
STEP 1. Using diagnostic tool , diagnose the CAN bus line.
To prevent damage to diagnostic tool (MUT-III), always turn
the ignition switch to the "LOCK" (OFF) position before
connecting or disconnecting diagnostic tool (MUT-III).
(1) Connect diagnostic tool 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-15).
STEP 2. Using diagnostic tool , read the Electronic control
unit diagnostic trouble code.
Check whether any engine or automatic transmission DTCs are
set or not.
(1) Turn the ignition switch to the "ON" position.
(2) Check for engine and automatic transmission DTCs.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?
YES : Go to Step 3.
NO : Refer to GROUP 13A, Diagnostic Trouble Code
13A-17.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-66
STEP 3. Using diagnostic tool , check for any diagnostic
trouble code.
Check if a DTC, which relates to CAN communication-linked
systems below, is set.
Combination meter
DTC indicating a time-out error related to the engine or
automatic transmission control system
ETACS
DTC indicating a time-out error related to the engine or
automatic transmission control system
Multi-center display unit
DTC indicating a time-out error related to the engine or
automatic transmission control system
(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 5.
NO : Go to Step 4.
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 Electronic control unit. On completion,
check that the DTC is not reset.
NO : There is an intermittent malfunction such as poor
engaged connector(s) or open circuit (Refer to
GROUP 00, How to Use Troubleshooting/Inspection
Service Points
How to Cope with Intermittent
Malfunctions P.00-14).

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-67
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
Electronic control unit and the A/C-ECU (Refer to
GROUP 00, How to Use Troubleshooting/Inspection
Service Points
How to Cope with Intermittent
Malfunctions P.00-14.)
NO : Replace the A/C-ECU. On completion, check that the
DTC is not reset.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-68
SYMPTOM CHART M1552009900495
During diagnosis, a DTC code associated with
other system may be set when the ignition switch
is turned on with connector(s) disconnected. On
completion, confirm all systems for DTC code(s).
If DTC code(s) are set, erase them all.
SYMPTOM INSPECTION
PROCEDUREREFERENCE
PA G E
When the ignition switch is "ON", the A/C does not operate. 1.
P.55-69
When the air outlet changeover control knob is moved to DEFROSTER or
DEFROSTER/FOOT position, the A/C or the inside/outside air
changeover damper motor does not operate.2.
P.55-69
Outside/Inside air changeover is not possible. 3.
P.55-70
When the A/C is operating, temperature inside the passenger
compartment does not decrease (cool air is not emitted).4.
P.55-75
Blower fan and motor do not turn. 5.
P.55-89
Blower air amount cannot be changed. 6.
P.55-100
The A/C indicator flashes. 7.
P.55-104
Defogger function does not operate. 8.
P.55-110
Defogger timer function does not operate. 9.
P.55-121
Malfunction of the A/C-ECU power supply system. 10.
P.55-122
Condenser fan does not operate. 11. REFER TO
GROUP 14

SYMPTOM
CHART P.14-3
When sunlight intensity changes, air outlet temperature does not change. 12
P.55-128

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-69
SYMPTOM PROCEDURES
INSPECTION PROCEDURE 1: When the Ignition Switch is "ON", the A/C does not Operate.
.
TECHNICAL DESCRIPTION (COMMENT)
The blower system or the compressor system may
be defective if there is no cool air coming from the
vents.
.
TROUBLESHOOTING HINTS
Malfunction of blower motor
Malfunction of A/C compressor
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
DIAGNOSIS
Check that the blower motor operation when the blower
switch is moved to the "HI" position.
(1) Turn the ignition switch to the "ON" position.
(2) Turn the blower speed selection dial to the blower operating
position.
Q: Does the blower motor operate when the speed
selection dial is turned to the blower operating
position?
YES : Refer to Inspection procedure 4 "When the A/C is
operating, temperature inside the passenger
compartment does not decrease (cool air not emitted)
P.55-75."
NO : Refer to Inspection procedure 5 "Blower fan and
motor do not turn P.55-89."
INSPECTION PROCEDURE 2: When the Air Outlet Changeover Control Knob is Moved to
DEFROSTER or DEFROSTER/FOOT Position, the A/C or the Inside/outside Air Changeover Damper
Motor does not operate.
.
TECHNICAL DESCRIPTION (COMMENT)
If the outside/inside air selection damper control
motor does not operate normally, the inside/outside
air changeover damper motor system may be defec-
tive.
.
TROUBLESHOOTING HINTS
Malfunction of the A/C-ECU
Malfunction of the outside/inside air selection
damper control motor
Damaged harness wires or connectors
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-70
DIAGNOSIS
Check operation of the outside/inside air selection damper
control motor.
(1) Turn the ignition switch to the "ON" position.
(2) Outside/inside air selection damper motor switch: This is
used to switch from the inside air to outside air or vice
versa.
(3) Check to see that the outside/inside air selection damper
motor operates normally.
Q: Does outside/inside air selection damper control motor
work normally?
YES : Replace the A/C-ECU.
NO : Refer to Inspection procedure 3, "Inside/outside air
changeover is not possible P.55-70."
INSPECTION PROCEDURE 3: Outside/Inside Air Changeover is not possible.
.
CIRCUIT OPERATION
If the outside/inside air selection damper control
motor does not operate normally, the outside/inside
air selection damper control motor system may be
defective.
.
TROUBLESHOOTING HINTS
Malfunction of the outside/inside air selection
damper control motor
Malfunction of the A/C-ECU
Damaged harness wires or connectors
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
DIAGNOSIS
Required Special Tool:
MB991223: Test Harness Set
STEP 1. Check the defogger and A/C operations.
Q: Do the defogger and A/C work normally?
YES : Go to Step 2.
NO : Refer to Inspection procedure 10 "Malfunction of the
A/C-ECU power supply system P.55-122."