Mitsubishi Grandis. Manual — part 288

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-37

Step 3. Check the wiring harness between C-105
A/C-ECU connector (terminals 33 and 34) and
C-04 rear mode selection damper control motor
and potentiometer connector (terminals 1 and 2).

• Check the motor activating lines for open or short

circuit.

Q: Is the check result normal?

YES :

Go to Step 4.

NO :

Repair the wiring harness.

Step 4. Check the rear mode selection damper
control motor and potentiometer.

Refer to

P.55-208

.

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Replace the mode selection damper control
motor and potentiometer.

Step 5. MUT-III diagnosis code

Q: Is the diagnosis code set?

YES :

Replace the automatic air conditioner

control panel (A/C-ECU)

NO :

The trouble can be an intermittent
malfunction (Refer to GROUP 00, How to
Cope with Intermittent Malfunction

P.00-5

.)

AC310614

AJ

Connectors: C-04, C-105 <LHD>

Harness side

C-105

C-04

C-105

Harness side

C-04 (GR)

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

AC310632 AE

Connectors: C-04, C-105 <RHD>

Harness side

C-105

C-04

C-105

Harness side

C-04 (GR)

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-38

Code No.U1073 Bus off error

CAUTION

If diagnosis code No. U1073 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

If the A/C-ECU ceases communicating once (i.e. bus
off) and then returns to it, the combination meter will
not communicate for three minutes immediately after
that point. This three-minute period is called "Penalty
mode." Immediately after the combination meter
returns to communication, the diagnosis code is set.

COMMENTS ON TROUBLE SYMPTOM

The wiring harness wire or connectors may have
loose, corroded, or damage terminals, or terminals
pushed back in the connector, or the A/C-ECU may
be defective.

POSSIBLE CAUSES

• Damaged harness wires and connectors

• Malfunction of the A/C-ECU

Step 1. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 2

NO :

Repair the CAN bus lines. (Refer to GROUP
54D

− Troubleshooting

P.54D-16

.) On

completion, go to Step 3.

Step 2. MUT-III diagnosis code.

Recheck if the diagnosis code is set.

1. Erase the diagnosis code.
2. Ignition switch: LOCK (OFF) to ON
3. Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES :

Replace the A/C-ECU, and then go to Step

3 .

NO :

If a trouble is solved, it is determined that
there is an intermittent malfunction such as
poor engaged connector(s) or open circuit.
(Refer to GROUP 00, How to Cope with
Intermittent Malfunction

P.00-5

.)

Step 3. MUT-III diagnosis code

Recheck if the diagnosis code is set.

1. Erase the diagnosis code.
2. Ignition switch: LOCK (OFF) to ON
3. Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES :

Return to Step 1.

NO :

The procedure is complete.

Code No.U1100: Engine CAN communication time-out

CAUTION

If diagnosis code No. U1100 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

U1100

• A/C-ECU receives engine control system-related

signals from the engine-ECU <M/T> or the
engine-A/T-ECU <A/T> via CAN bus lines. If the
display unit can not receive the necessary
signals, diagnosis code U1100 will be set.

COMMENTS ON TROUBLE SYMPTOM

Current trouble

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

lines between the engine-ECU <M/T>,
engine-A/T-ECU <A/T> and the A/C-ECU, the
power supply system to the engine-A/T-ECU, the
A/C-ECU, the engine-ECU <M/T> or the
engine-A/T-ECU <A/T> may be defective.

Past trouble

• Carry out diagnosis with particular emphasis on

connector(s) or wiring harness in the CAN bus
lines between the engine-ECU <M/T>,
engine-A/T-ECU <A/T> and the A/C-ECU, the
power supply system to the engine-ECU <M/T>

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-39

or the engine-A/C-ECU <A/T>. For diagnosis
procedures, refer to "How to cope with past
trouble" (Refer to GROUP 00

− How to Use

Troubleshooting/Inspection Service Points

P.00-5

).

NOTE: For a past trouble, you can not find it by the

MUT-III CAN bus diagnostics even if there is any
failure in CAN bus lines. In this case, refer to
GROUP 00, How to Cope with Intermittent
Malfunctions

P.00-5

and check the CAN bus

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

−

Explanation about the MUT-III CAN bus

diagnostics

P.54D-9

).

CAUTION

If the ignition switch is turned to the ON position
without starting the engine, the diagnosis code
U1100 (past trouble) may be set to the A/C-ECU
after three minutes.

POSSIBLE CAUSES

• Damaged harness wires and connectors

• Malfunction of engine-ECU <M/T> or

engine-A/T-ECU <A/T>

• Malfunction of the A/C-ECU

Step 1. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 2.

NO :

Repair the CAN bus lines. (Refer to GROUP
54D

− Troubleshooting

P.54D-16

. Repair

the CAN bus line and then go to Step 6.

Step 2. MUT-III Diagnosis code of other systems

Check whether the engine-related diagnosis code is
set.

Q: Is the diagnosis code set?

YES :

Diagnose the engine control system. Refer

to

P.13A-20

.

NO :

Go to Step 3.

Step 3. MUT-III Diagnosis code of other systems

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

• Combination meter

U1100: Engine-related time-out diagnosis code

• Multi-centre display

U1100: Engine-related time-out diagnosis code

• ETACS

011 or 012: diagnosis code of engine-related

time-out

Q: Is the diagnosis code set?

YES :

Go to Step 4.

NO :

Go to Step 5.

Step 4. Check whether the diagnosis code is
reset.

Recheck if the diagnosis code is set.

1. Erase the diagnosis code.
2. Ignition switch: LOCK (OFF) to ON
3. Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES :

Replace the engine-ECU <M/T> or the

engine-A/T-ECU <A/T>, go to Step 6 .

NO :

A poor connection, open circuit or other
intermittent malfunction is present in the
CAN bus lines between the engine-ECU
<M/T> or the engine-A/T-ECU <A/T> and
the A/C-ECU. (Refer to GROUP 00, How to
Cope with Intermittent Malfunction

P.00-5

.)

Step 5. Check whether the diagnosis code is
reset.

Recheck if the diagnosis code is set.

1. Erase the diagnosis code.
2. Ignition switch: LOCK (OFF) to ON
3. Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES :

Replace the A/C-ECU, and then go to Step

6 .

NO :

A poor connection, open circuit or other
intermittent malfunction is present in the
CAN bus lines between the engine-ECU
<M/T> or the engine-A/T-ECU <A/T> and
the A/C-ECU. (Refer to GROUP 00, How to
Cope with Intermittent Malfunction

P.00-5

.)

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-40

Step 6. Check whether the diagnosis code is
reset.

Recheck if the diagnosis code is set.

1. Erase the diagnosis code.
2. Ignition switch: LOCK (OFF) to ON
3. Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES :

Return to Step 1.

NO :

The procedure is complete.

Code No.U1109: ETACS related CAN communication time-out

CAUTION

If diagnosis code No. U1109 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 air conditioner
operation-related signal from the ETACS-ECU via
the CAN bus lines. If the A/C-ECU can not receive
the air conditioner operation-related signal at all on
the ETACS-ECU, diagnosis code No.U1109 will be
set.

COMMENTS ON TROUBLE SYMPTOM

Current trouble

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

lines between the ETACS-ECU and the
A/C-ECU, the power supply system to the
ETACS-ECU, the ETACS-ECU itself, or the
A/C-ECU may be defective.

Past trouble

• Carry out diagnosis with particular emphasis on

connector(s) or wiring harness in the CAN bus
lines between the ETACS-ECU and the
A/C-ECU, and the power supply system to the
ETACS-ECU. For diagnosis procedures, refer to
"How to cope with past trouble" (Refer to GROUP
00

− How to Use Troubleshooting/Inspection

Service Points

P.00-5

).

NOTE: For a past trouble, you can not find it by the

MUT-III CAN bus diagnostics even if there is any
failure in CAN bus lines. In this case, refer to
GROUP 00

−

How to Cope with Intermittent

Malfunctions

P.00-5

and check the CAN bus

lines. You can narrow down the possible cause of

the trouble by referring to the diagnosis code,
which is set regarding the CAN
communication-linked ECUs (Refer to GROUP
54D

−

Explanation about the MUT-III CAN bus

diagnostics

P.54D-9

).

CAUTION

If the ignition switch is turned to the ON position
without starting the engine, the diagnosis code
U1109 (past trouble) may be set to the A/C-ECU
after three minutes.

POSSIBLE CAUSES

• Damaged harness wires and connectors

• Malfunction of ETACS-ECU

• Malfunction of the A/C-ECU

Step 1. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 2

NO :

Repair the CAN bus lines. (Refer to GROUP
54D

− Troubleshooting

P.54D-16

.) On

completion, go to Step 6.

Step 2. MUT-III Diagnosis code of other systems

Check whether the ETACS-related diagnosis code is
set.

Q: Is the diagnosis code set?

YES :

Diagnose the ETACS-ECU. Refer to

P.54B-29

.

NO :

Go to Step 3

Step 3. MUT-III Diagnosis code of other systems

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

• combination meter

U1109: ETACS-related time-out diagnosis code

Q: Is the diagnosis code set?