Mitsubishi Grandis. Manual - part 290

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-45

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: Communication with the MUT-III is not possible.

COMMENTS ON TROUBLE SYMPTOM

If communication with all other systems is not 
possible, there is a high possibility that there is a 
malfunction of the diagnosis line. If only the A/C 
system can not communicate with the MUT-III, the 
A/C-ECU may be defective.

POSSIBLE CAUSES

• Malfunction of the A/C-ECU

ENGINE-ECU <M/T>
OR
ENGINE-ECU <A/T>

DIAGNOSIS
CONNECTOR

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 : Gray     R : Red     P : Pink     V : Violet

NOTE

: LHD
: RHD

FRONT SIDE

A/C-ECU CAN-BAS Line Circuit

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-46

DIAGNOSIS

Step 1. Check that Engine-A/T-ECU 
communicates with the MUT-III

Use the MUT-III to confirm that it communicates with 
the engine-A/T-ECU.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Diagnose the MPI system. Refer to GROUP 
13A 

− Troubleshooting 

P.13A-20

.

Step 2. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES <RHD> : 

INSPECTION PROCEDURE 26: 

Refer to A/C-ECU power supply system 
<LHD>

P.55-174

 .

YES <LHD> : 

INSPECTION PROCEDURE 27: 

Refer to A/C-ECU power supply system 
<RHD>

P.55-178

 .

NO : 

Repair the CAN bus line (Refer to GROUP 
54D - Troubleshooting 

P.54D-16

).

INSPECTION PROCEDURE 2: Cool air does not come

CIRCUIT OPERATION

If the blower air temperature can not be cool when 
turning A/C switch ON and lowering the preset 
temperature, inadequate refrigerant quantity, 
sensors, harness or connectors may be suspected.

POSSIBLE CAUSES

• Damaged the wiring harness or connectors

Step 1. Check the blower operation
(1) Turn the ignition switch to the ON position.
(2) Blower knob: Other than OFF
(3) Check that the air comes out of the blower.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Refer to Inspection Procedure 3 " Front 
blower does not work 

P.55-47

".

Step 2. Check the A/C compressor operation

Check that the compressor operates under the 
following conditions.

• Engine operation

• Air conditioner switch: ON

• Temperature control dial: 18°C (MAX COOL)

Q: Is the check result normal?

YES : 

Go to Step 3.

NO <LHD> : 

Refer to Inspection Procedure 7 " 

Front compressor does not work 
<LHD>

P.55-71

  ".

NO <RHD> : 

Refer to Inspection Procedure 8 " 

Front compressor does not work 
<RHD>

P.55-78

  ".

Step 3. MUT-III diagnosis code

Check that the diagnosis code related to the air 
conditioner is not set.

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Carry out the diagnosis code procedures. 
Refer to 

P.55-8

.

Step 4. MUT-III data list

Check that the following service data MUT-III display 
contents are normal.

• Item 04: Pressure sensor

• Item 50: Front preset temperature

Q: Is the check result normal?

YES : 

Go to Step 5.

NO <Item 04 is abnormal> : 

Inspection Procedure 

18: Refer to A/C pressure sensor system 

P.55-142

 <LHD> or Inspection Procedure 

19: Refer to A/C pressure sensor system 

P.55-144

 <RHD>.

NO <Item 50 is abnormal> : 

Replacement of the 

A/C-ECU

STEP 5. Refrigerant level check
Check that the refrigerant level is adequate. Refer to 

P.55-193

.

Q: Is the check result normal?

YES : 

Intermittent malfunction. (Refer to GROUP 

00 

− How to Cope with Intermittent 

Malfunction 

P.00-5

.)

NO : 

Charge or remove the refrigerant level. 
Refer to 

P.55-191

 or 

P.55-190

.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-47

INSPECTION PROCEDURE 3: The front blower does not work

COMMENTS ON TROUBLE SYMPTOM

If the blower motor does not operate, the blower 
motor circuit system may be defective.

POSSIBLE CAUSES

• Malfunction of the front blower motor (blower 

linear controller).

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

FUSIBLE
LINK

30

IGNITION
SWITCH (IG2)

FRONT
BLOWER
RELAY

A/C-ECU

A/C-ECU

FRONT BLOWER
MOTOR

FRONT
POWER
TRANSISTOR

Blower Motor Circuit

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-48

• Malfunction of the automatic air conditioner 

control panel (A/C-ECU)

• Damaged the wiring harness or connectors

DIAGNOSIS

Step 1. Check the operation of the heater control 
panel

Check that the A/C switch, rear window defogger 
switch and outside/inside air selection switch can 
operate.

Q: Is the check result normal?

YES <RHD> : 

INSPECTION PROCEDURE 26: 

Refer to A/C-ECU power supply system 
<LHD>

P.55-174

  .

YES <LHD> : 

INSPECTION PROCEDURE 27: 

Refer to A/C-ECU power supply system 
<RHD>

P.55-178

  .

NO : 

Repair the CAN bus line (Refer to GROUP 
54D - Troubleshooting 

P.54D-16

.)

Step 2. MUT-III actuator test

Carry out the actuator test.

• Item 01, 02, 03: Front blower fan

Q: Does the blower motor work normally? 

YES : 

Go to Step 3.

NO : 

Go to Step 4.

Step 3. Recheck the trouble symptom

Q: Is the check result normal?

YES : 

Intermittent malfunction. (GROUP 00 

− How 

to Cope with Intermittent Malfunction 

P.00-5

)

NO : 

Replace the air conditioner control panel 
(A/C-ECU) or the blower motor (blower 
linear controller).

Step 4. Connector check: C-209 front blower 
relay connector

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the connector.

Step 5. Check the blower relay.

Refer to GROUP 55, On-vehicle Service 

− Power 

relay check 

P.55-196

.

Q: Is the blower relay in good condition?

YES : 

Go to Step 6.

NO : 

Replace the blower relay.

AC310623

Connector: C-209 <LHD>

AD

3

4

5

1

2

Junction block side

Junction block (Front view)

AC310618

Connector: C-209 <RHD>

AD

3

4

5

1

2

Junction block side

Junction block (Front view)