Mitsubishi Lancer (4A9 engine). Manual - part 297

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-69

INSPECTION PROCEDURE 11: A/C pressure sensor system

A/C Pressure Sensor Circuit

A/C PRESSURE
SENSOR

A/C-ECU

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

ACB02625

AC612691

AE

Connector: A-47

A-47 (B)

AC612706

Connector: C-15 <LHD>

AK

C-15 (B)

ACB02645

Connector: C-127 <LHD>

AB

C-127 (GR)

ACB02648

AB

C-15 (B)

C-127 (GR)

Connectors: C-15, C-127 <RHD>

COMMENTS ON TROUBLE SYMPTOM
If the A/C pressure sensor system is defective, the 
wiring harness between the A/C pressure sensor and 
the A/C-ECU is suspected.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-70

PROBABLE CAUSES

• Malfunction of the A/C pressure sensor

• Malfunction of the A/C-ECU

• Damaged wiring harness or connectors

DIAGNOSTIC PROCEDURE

STEP 1. Connector check: A-47 A/C pressure 
sensor connector

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector concerned.

STEP 2. Inspection of the A/C pressure sensor
Refer to .

Q: Is the A/C pressure sensor normal?

YES : 

Go to Step 3.

NO : 

Replace the A/C pressure sensor.

STEP 3. Connector check: C-15 A/C-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Repair the connector concerned.

STEP 4. Check the wiring harness wires between 
A-47 A/C pressure sensor connector (terminals 3, 
2 and 1) and C-15 A/C-ECU connector (terminals 
20, 16 and 19).

• Check the input line for open circuit.

NOTE: Prior to the wiring harness inspection, inter-
mediate connector C-127, and repair if necessary.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the wiring harness.

STEP 5. Retest the system.

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 A/C-ECU.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-71

INSPECTION PROCEDURE 12: Blower motor power supply system

Blower Motor Circuit

FUSIBLE
LINK

37

BLOWER
RELAY

ETACS-
ECU 

A/C-ECU

BLOWER
MOTOR

POWER
TRANSISTOR

NOTE

: LHD
: RHD

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

FUSIBLE
LINK

42

<4N1>

<4A9, 4J1, 4B1>

ACB02688

AC612706

Connector: C-110 <LHD>

AL

AC612710

Connector: C-110 <RHD>

BB

AC612709

Connectors: C-303, C-309, C-315 <LHD>

AS

C-309 (B)

C-303

C-315

ETACS-ECU

AC612717

Connectors: C-303, C-309, C-315 <RHD>

AS

C-309 (B)

C-315

ETACS-ECU

C-303

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-72

COMMENTS ON TROUBLE SYMPTOM
If the blower motor is not energised, the blower relay 
system is suspected.

PROBABLE CAUSES

• Malfunction of the blower relay

• Damaged wiring harness or connectors

• Malfunction of the ETACS-ECU

DIAGNOSTIC PROCEDURE

STEP 1. Connector check: C-303 blower relay 
connector

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector concerned.

STEP 2. Measure the voltage at C-303 blower 
relay connector.
(1) Remove the relay, and measure at the junction 

block side.

(2) Voltage between terminals 1, 4 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Go to Step 3.

STEP 3. Check the wiring harness between C-303 
blower relay connector terminal No. 4, 1 and 
fusible link (37) <Petrol engine> or fusible link 
(42) <Diesel engine>.

• Check the power supply line for open circuit.

NOTE: Prior to the wiring harness inspection, check 
ETACS-ECU connector C-309, and repair if neces-
sary.

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 4. Connector check: C-110 blower motor 
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-110 
blower motor connector terminal No. 1 <LHD> or 
2 <RHD> and C-303 blower relay connector 
terminal No. 3.
NOTE: Prior to the wiring harness inspection, check 
junction block connector C-315, and repair if neces-
sary.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the wiring harness.