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?