Mitsubishi Lancer (4A9 engine). Manual - part 287

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-29

YES : 

Diagnose the ETACS-ECU. Refer to .

NO : 

Go to Step 3

STEP 3. M.U.T.-III other system diagnosis code
Check if a diagnosis code, which relates to CAN 
communication-linked systems below, is set.

• ETACS-ECU

U0141: ETACS-related time-out diagnosis code

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 ETACS-ECU, and then go to 

Step 6.

NO : 

A poor connection, open circuit or other 
intermittent malfunction in the CAN bus line 
between the ETACS-ECU and the A/C-ECU 
(Refer to GROUP 00 

− How to Cope with 

Intermittent Malfunction ).

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 in the CAN bus line 
between the ETACS-ECU and the A/C-ECU 
(Refer to GROUP 00 

− How to Cope with 

Intermittent Malfunction ).

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. U0151: SRS CAN time-out

CAUTION

If diagnosis code No.U0151 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 control-related 
signals from the SRS-ECU via the CAN bus lines. If 
the ECU cannot receive any of the air conditioner 
control-related signals from the SRS-ECU, diagnosis 
code U0151 will be stored.

COMMENTS ON TROUBLE SYMPTOM

Current trouble

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

lines between the SRS-ECU and the A/C-ECU, 
the power supply system to the SRS-ECU, the 
SRS-ECU itself, or the A/C-ECU may be defec-
tive.

Past trouble

• Carry out diagnosis with particular emphasis on 

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

− How to Treat 

Past Trouble ). 

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

M.U.T.-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 Mal-
function  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 54C 

−

 CAN Bus Line Diagnos-

tic Flow ).

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-30

CAUTION

If the ignition switch is turned to the ON position 
without starting the engine, the diagnosis code 
U0151 (past trouble) may be set to the A/C-ECU 
after three minutes.

PROBABLE CAUSES

• Damaged wiring harness or connectors

• Malfunction of the SRS-ECU 

• Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-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 
54C, Troubleshooting ) On completion, go to 
Step 6.

STEP 2. M.U.T.-III other system diagnosis code
Check whether the SRS-related diagnosis code is 
set.

Q: Is the diagnosis code set?

YES : 

Diagnose the SRS-ECU. Refer to .

NO : 

Go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code
Check if a diagnosis code, which relates to CAN 
communication-linked systems below, is set.

• SRS-ECU

U0151: SRS-ECU-related time-out diagnosis code

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 SRS-ECU, and then go to Step 

6.

NO : 

A poor connection, open circuit or other 
intermittent malfunction in the CAN bus line 
between the SRS-ECU and the A/C-ECU 
(Refer to GROUP 00 

− How to Cope with 

Intermittent Malfunction ).

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 in the CAN bus line 
between the SRS-ECU and the A/C-ECU 
(Refer to GROUP 00 

− How to Cope with 

Intermittent Malfunction ).

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. U0155: Meter CAN time-out

CAUTION

If diagnosis code No.U0155 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 control-related 

signals from the combination meter via the CAN bus 
lines. If the ECU cannot receive any of the air condi-
tioner control-related signals from the combination 
meter, diagnosis code U0155 will be stored.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-31

COMMENTS ON TROUBLE SYMPTOM

Current trouble

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

lines between the combination meter and the A/
C-ECU, the power supply system to the combina-
tion meter, the combination meter itself, or the A/
C-ECU may be faulty.

Past trouble

• Carry out diagnosis with particular emphasis on 

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

− 

How to Treat Past Trouble ).

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

M.U.T.-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 Mal-
function  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 54C 

−

 CAN Bus Line Diagnos-

tic Flow ).

CAUTION

If the ignition switch is turned to the ON position 
without starting the engine, the diagnosis code 
U0168 (past trouble) may be set to the A/C-ECU 
after three minutes.

PROBABLE CAUSES

• Damaged wiring harness or connectors

• Malfunction of the combination meter 

• Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-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 
54C, Troubleshooting ). On completion, go 
to Step 6.

STEP 2. M.U.T.-III other system diagnosis code
Check whether the combination meter-related diag-
nosis code is set.

Q: Is the diagnosis code set?

YES : 

Diagnose the combination meter. Refer to .

NO : 

Go to Step 3

STEP 3. M.U.T.-III other system diagnosis code
Check if a diagnosis code, which relates to CAN 
communication-linked systems below, is set.

• Combination meter

U0155: Combination meter-related time-out diagno-

sis code

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 combination meter, and then 

go to Step 6.

NO : 

A poor connection, open circuit or other 
intermittent malfunction in the CAN bus line 
between the combination meter and the A/
C-ECU (Refer to GROUP 00 

− How to Cope 

with Intermittent Malfunction ).

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 in the CAN bus line 
between the combination meter and the A/
C-ECU (Refer to GROUP 00 

− How to Cope 

with Intermittent Malfunction ).

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?

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-32

YES : 

Return to Step 1.

NO : 

The procedure is complete.

Code No. U0168: WCM CAN time-out

CAUTION

If diagnosis code No.U0168 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 control-related 
signals from the WCM via the CAN bus lines. If the 
ECU cannot receive any of the air conditioner con-
trol-related signals from the WCM, diagnosis code 
U0168 will be stored.

COMMENTS ON TROUBLE SYMPTOM

Current trouble

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

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

Past trouble

• Carry out diagnosis with particular emphasis on 

connector(s) or wiring harness in the CAN bus 
lines between the A/C-ECU and the WCM, and 
the power supply system to the WCM. For diag-
nosis procedures, refer to "How to treat past trou-
ble" (Refer to GROUP 00 

− How to Treat Past 

Trouble ).?

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

M.U.T.-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 Mal-
function  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 54C 

−

 CAN Bus Line Diagnos-

tic Flow ).

CAUTION

If the ignition switch is turned to the ON position 
without starting the engine, the diagnosis code 
U0168 (past trouble) may be set to the A/C-ECU 
after three minutes.

PROBABLE CAUSES

• Damaged wiring harness or connectors

• Malfunction of the WCM 

• Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-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 
54C Troubleshooting ). On completion, go to 
Step 6.

STEP 2. M.U.T.-III other system diagnosis code
Check whether the WCM-related diagnosis code is 
set.

Q: Is the diagnosis code set?

YES : 

Diagnose the WCM. Refer to .

NO : 

Go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code
Check if a diagnosis code, which relates to CAN 
communication-linked systems below, is set.

• WCM

U0168: WCM-related time-out diagnosis code

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 WCM, and then go to Step 6.

NO : 

A poor connection, open circuit or other 
intermittent malfunction in the CAN bus line 
between the WCM and the A/C-ECU (Refer 
to GROUP 00 

− How to Cope with 

Intermittent Malfunction ).