2005 MITSUBISHI 380 service

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 VENTILATION55-66
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 VENTILATION55-72
NOTE: Also check junction block connectors C-211(terminal
16) and C-215 (terminal 2) for loose, corroded, or damaged ter-
minals, or terminals pushed back in the connector. If junction
block connector C-211 or C-215 is damaged, repair or replace
the connector as described in GROUP 00E, Harness Connec-
tor Inspection P.00E-2.
Q: Is the wiring harness between outside/inside air
selection damper control motor connector C-106
(terminal 1) and the ignition switch (IG2) in good
condition?
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 : Repair the wiring harness. Check that the
outside/inside air selection damper control motor
works normally.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-74
STEP 7. Check the wiring harness between outside/inside
air selection damper control motor connector C-106
(terminals 5 and 7) and A/C-ECU C-15 (terminals 5 and 6).
Q: Are the wiring harness between outside/inside air
selection damper control motor connector C-106
(terminals 4 and 5) and A/C-ECU C-16 (terminals 5 and
6) in good condition?
YES : Go to Step 8.
NO : Repair the wiring harness. Check that the
outside/inside air selection damper control motor
works normally.
STEP 8. Retest the system.
Q: Does a malfunction take place again?
YES : Replace the A/C-ECU, and check that the
outside/inside air selection damper control motor
works normally.
NO : 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.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-81
NOTE: Also check intermediate connector A-13, junction block
connectors C-214 and C-215 for loose, corroded, or damaged
terminals, or terminals pushed back in the connector. If inter-
mediate connector A-13, junction block connector C-214 or
C-215 is damaged, repair or replace the connector as
described in GROUP 00E, Harness Connector Inspection
P.00E-2.
Q: Is the wiring harness between A/C compressor clutch
relay connector B-18X (terminal 2) and the ignition
switch (IG2) in good condition?
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 : Repair the wiring harness. Check that the air
conditioning works normally.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-83
NOTE: Also check intermediate connector A-13 for loose, cor-
roded, or damaged terminals, or terminals pushed back in the
connector. If intermediate connector A-13 is damaged, repair or
replace the connector as described in GROUP 00E, Harness
Connector Inspection P.00E-2.
Q: Is the wiring harness between A/C compressor clutch
relay connector B-18X (terminal 1) and the battery in
good condition?
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 : Repair the wiring harness. Check that the air
conditioning works normally.
STEP 13. Check the wiring harness between A/C
compressor clutch relay connector B-18X (terminal 4) and
A/C compressor assembly connector B-28 (terminal 1).
Q: Is the wiring harness between A/C compressor clutch
relay connector B-18X (terminal 4) and A/C compressor
connector B-28 (terminal 1) in good condition?
YES : Go to Step 14.
NO : Repair the wiring harness. Check that the air
conditioning works normally.