Mitsubishi Lancer (4A9 engine). Manual - part 285

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-21

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-119 A/C control 
panel connector and C-15 A/C-ECU connector

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector.

STEP 2. Check the wiring harness between C-119 
A/C control panel connector terminal No. 9 and 
C-15 A/C-ECU connector terminal No. 9.

• Check the A/C control panel signal line for open 

or short circuit.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the wiring harness.

STEP 3. Check whether the diagnosis code is 
reset
Replace the A/C control panel, and erase the diagno-
sis code. Then check that no diagnosis code is being 
set.

Q: Is the diagnosis code set?

YES : 

Replace the A/C-ECU.

NO : 

This diagnosis is complete.

Code No. B1021: Fan dial SW error <Vehicles without A/C>

Heater Control Panel Circuit

HEATER 
CONTROL 
UNIT

HEATER 
CONTROL 
PANEL

CPU

INTERFACE
CIRCUIT

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

ACA00851

AC612706

Connectors: C-60, C-147 <LHD>

BP

C-60 (B)

C-147

COMMENTS ON TROUBLE SYMPTOM
This code will be set when the air volume control dial 
position on the AC control panel is detected as 
abnormal.

PROBABLE CAUSES

• Malfunction of the heater control panel

• Damaged wiring harness or connectors

• Malfunction of the heater control unit

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-22

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-147 heater control 
panel connector and C-60 heater control unit 
connector

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector.

STEP 2. Check the wiring harness between C-147 
heater control panel connector terminal No. 9 
and C-60 heater control unit connector terminal 
No. 9.

• Check the heater control panel signal line for 

open or short circuit.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the wiring harness.

STEP 3. Check whether the diagnosis code is 
reset.
Replace the heater control panel, and erase the 
diagnosis code. Then check that no diagnosis code 
is being set.

Q: Is the diagnosis code set?

YES : 

Replace the heater control unit.

NO : 

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

Code No. B1021: Fan dial SW error <Vehicles with A/C>

A/C Control Panel Circuit

A/C-ECU

A/C
CONTROL
PANEL

CPU

INTERFACE
CIRCUIT

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

ACA00799

AC612706

Connectors: C-15, C-119 <LHD>

AE

C-15 (B)

C-119

AC612710

Connector: C-15 <RHD>

AS

C-15 (B)

AC612711

Connector: C-119 <RHD>

AG

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-23

COMMENTS ON TROUBLE SYMPTOM
This code will be set when the air volume control dial 
position on the AC control panel is detected as 
abnormal.

PROBABLE CAUSES

• Malfunction of the A/C control panel

• Damaged wiring harness or connectors

• Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-119 A/C control 
panel connector and C-15 A/C-ECU connector

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector.

STEP 2. Check the wiring harness between C-119 
A/C control panel connector terminal No. 9 and 
C-15 A/C-ECU connector terminal No. 9.

• Check the A/C control panel signal line for open 

or short circuit.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the wiring harness.

STEP 3. Check whether the diagnosis code is 
reset
Replace the A/C control panel, and erase the diagno-
sis code. Then check that no diagnosis code is being 
set.

Q: Is the diagnosis code set?

YES : 

Replace the A/C-ECU.

NO : 

This diagnosis is complete.

Code No. B1079: A/C Refrigerant leaks

COMMENTS ON TROUBLE SYMPTOM
If this code is set, the refrigerant level may not be 
appropriate, or the A/C pressure sensor may be 
faulty (If this code is set, the A/C indicator will flash).

PROBABLE CAUSES

• Inadequate refrigerant level 

• Malfunction of the A/C pressure sensor

• Malfunction of the ambient temperature sensor

• Damaged wiring harness or connectors

• Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the condenser assembly
Check that the condenser assembly is not wet.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Wait until the condenser is dry, and check 
that no diagnosis code is set.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-24

STEP 2. 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 3.

NO : 

Repair the CAN bus lines. (Refer to GROUP 
54C, Troubleshooting ). 

STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis code related to the A/C is 
not set.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis code procedures. 

Refer to . 

NO : 

Go to Step 4.

STEP 4. M.U.T.-III data list
Check that the following service data display con-
tents are normal. (Refer to )

• Item 02: Ambient temperature sensor

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Refer to code No.B1011, B1012: Ambient 
temperature sensor system .

STEP 5. Check the A/C pressure sensor
 Refer to .

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Replace the A/C pressure sensor.

STEP 6. Refrigerant level check
 Refer to .

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Correct the refrigerant level.

STEP 7. Check whether the diagnosis code is 
reset

Q: Is the diagnosis code set?

YES : 

Refer to Inspection Procedure 11: A/C 

pressure sensor system .

NO : 

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

Code No. B2214: Control panel failure <Vehicles without A/C>

Heater Control Panel Circuit

HEATER 
CONTROL 
UNIT

HEATER 
CONTROL 
PANEL

CPU

INTERFACE
CIRCUIT

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

ACA00851