Mitsubishi Lancer (4A9 engine). Manual - part 298

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-73

STEP 6. Retest the system.
 Check that the blower motor is energised.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Replace the ETACS-ECU.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-74

INSPECTION PROCEDURE 13: A/C-ECU power supply system

A/C-ECU Power Source Circuit

IGNITION 
SWITCH (IG1)

A/C-ECU

ETACS-
ECU

IG1 
RELAY

FUSIBLE 
LINK

<4N1>

38

FUSIBLE 
LINK

<4A9, 4J1, 4B1>

36

FUSIBLE 
LINK

<4N1>

44

FUSIBLE 
LINK

<4A9, 4J1, 4B1>

34

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

ENGINE 
COMPARTMENT

RELAY BOX

POWER 
SOURCE

POWER 
SOURCE

NOTE

:LHD
:RHD

ACB02703

ACA00894

Connector: C-15,  C-150 <LHD>

AC

C-15 (B)

C-150 (GR)

AC612710

Connector: C-15 <RHD>

AS

C-15 (B)

AC612711

Connector: C-150 <RHD>

DM

C-150 (GR)

AC612709

AU

Connector: C-317 <LHD>
ETACS-ECU

AC612717

Connector: C-317 <RHD>

AU

ETACS-ECU

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-75

COMMENTS ON TROUBLE SYMPTOM
If the A/C-ECU is not energised, the power supply or 
earth system to the ECU may be defective.

PROBABLE CAUSES

• Malfunction of the A/C-ECU

• Damaged wiring harness or connectors

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III other system's diagnosis code
Check that the ETACS-ECU has not set a diagnosis 
code.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis code procedures . 

Refer to GROUP 54A, ETACS-ECU .

NO : 

Go to Step 2.

STEP 2. Connector check: C-15 A/C-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the connector concerned.

STEP 3. Measure the voltage at the C-15 A/C-ECU 
connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Ignition switch: ON
(3) Voltage between terminal No. 15 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Go to Step 4.

STEP 4. Connector check: C-317 ETACS-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the connector concerned.

STEP 5. Check the wiring harness between C-15 
A/C-ECU connector terminal No. 15 and C-317 
ETACS-ECU connector terminal No. 5.

• Check the power supply line for open circuit.

NOTE: Prior to the wiring harness inspection, check 
joint connector C-150, and repair if necessary.

Q: Is the check result normal?

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-76

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

STEP 6. Measure the voltage at the C-15 A/C-ECU 
connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Voltage between terminal No. 13 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Go to Step 7.

STEP 7. Check the wiring harness between C-15 
A/C-ECU connector terminal No. 13 and C-317 
ETACS-ECU connector terminal No. 10.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

STEP 8. Measure the resistance at the C-15 A/C-
ECU connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Resistance between terminal No. 14 and body 

earth

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Replace the A/C-ECU.

NO : 

Go to Step 9.

STEP 9. Check the wiring harness between C-15 
A/C-ECU connector terminal No. 14 and body 
earth.

• Check the earth wires for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.