If communication with all other systems is not possi-
ble, there is a high possibility that there is a malfunc-
tion of the diagnosis line. If only the A/C system can
not communicate with the M.U.T.-III, the heater con-
troller assembly (A/C-ECU) may be defective.

PROBABLE CAUSE

Malfunction of the heater controller assembly
(A/C-ECU)

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 tem-
perature, inadequate refrigerant quantity, sensors,
harness or connectors may be suspected.

PROBABLE CAUSE

Damaged wiring harness or connectors

DIAGNOSIS PROCEDURE

STEP 1. Check the blower operation
Check that air blows through the air outlets.
(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 "The
blower does not work

P.55-21

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-21

STEP 2. Check the A/C compressor operation
Check that the compressor operates under the fol-
lowing conditions.

• Engine operation

• Air conditioner switch: ON

• Blower knob: Maximum air volume

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

NOTE: The compressor does not work when the
blower intake temperature is 0

C or less.

Q: Is the check result normal?

YES :

Go to Step 3.

NO :

Refer to Inspection Procedure 6 "The A/C
compressor does not work

P.55-23

STEP 3. 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 4.

NO :

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

− Troubleshooting ).

STEP 4. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES :

Carry out the diagnosis code procedures.

Refer to

P.55-7

NO :

Go to Step 5.

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

P.55-34

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00, How to Cope with Intermittent
Malfunction ).

NO :

Charge or remove the refrigerant level.
Refer to

P.55-34

INSPECTION PROCEDURE 3: The blower does not work

COMMENTS ON TROUBLE SYMPTOM

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

PROBABLE CAUSES

• Malfunction of the blower motor

• Malfunction of the power transistor

• Malfunction of the heater controller assembly

(A/C-ECU)

• Damaged wiring harness or connectors

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 ).

STEP 2. M.U.T.-III diagnosis code.
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 :

Carry out the diagnosis code procedures.

Refer to

P.55-7

NO :

Go to Step 3.

STEP 3. Check the blower relay.
Refer to

P.55-41

Q: Is the blower relay in good condition?

YES :

Go to Step 4.

NO :

Replace the blower relay.

STEP 4. Check the blower motor.
Refer to

P.55-48

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Replace the blower motor.

STEP 5. Voltage measurement at blower motor
connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Turn the ignition switch to the ON position.
(3) Voltage between terminal 1 and body earth.

OK: System voltage

Q: Is the check result normal?

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-22

YES :

Go to Step 6.

NO :

INSPECTION PROCEDURE 14: Refer to
"Blower motor power supply system"

P.55-27

STEP 6. Resistance measurement at the C-109
power transistor connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Continuity between terminal 1 and body earth

OK: Continuity exists (2

Ω or less)

Q: Is the check result normal?

YES :

Go to Step 7.

NO :

Repair the wiring harness wires between
power transistor connector terminal No. 1
and body earth.

STEP 7. Check of open circuit in power transistor
power supply line between blower motor and
power transistor connector.

Q: Is the check result normal?

YES :

Go to Step 8.

NO :

Repair the connector(s) or wiring harness.

STEP 8. Check of open circuit in P/TB and P/TC
line between blower motor, power transistor and
heater controller assembly (A/C-ECU) connector.

Q: Is the check result normal?

YES :

Go to Step 9.

NO :

Repair the connector(s) or wiring harness.

STEP 9. Replace the power transistor and
recheck the trouble symptom
Check that the blower motor operates normally.

Q: Is the check result normal?

YES :

This diagnosis is complete.

NO :

Replace the heater controller assembly
(A/C-ECU).

INSPECTION PROCEDURE 4: The blower air volume cannot be changed

COMMENTS ON TROUBLE SYMPTOM

If air volume cannot be adjusted by using the blower
control, the A/C control panel, the heater controller
assembly (A/C-ECU) or the power transistor may be
faulty.

PROBABLE CAUSES

• Malfunction of the power transistor

• Damaged wiring harness or connectors

• Malfunction of the heater controller assembly

(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 ).

STEP 2. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES :

Carry out the diagnosis code procedures.

Refer to

P.55-7

NO :

Go to Step 3.

STEP 3. Resistance measurement at the power
transistor connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Continuity between terminal 1 and body earth

OK: Continuity exists (2

Ω or less)

Q: Is the check result normal?

YES :

Go to Step 4.

NO :

Repair the wiring harness wires between
power transistor connector terminal No. 1
and body earth.

STEP 4. Check of open circuit in P/TB, P/TC and
E line between blower motor, power transistor,
earth J/C(DASH) and heater controller assembly
(A/C-ECU) connector.

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Repair the connector(s) or wiring harness.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-23

STEP 5. Replace the power transistor and
recheck the trouble symptom
Check that the blower motor operates normally.

Q: Is the check result normal?

YES :

This diagnosis is complete.

NO :

Replace the heater controller assembly
(A/C-ECU).

INSPECTION PROCEDURE 5: The Inside/Outside Air Changeover is impossible.

COMMENTS ON TROUBLE SYMPTOM

If the air recirculation cannot be changed by using
the inside air/outside air changeover switch, the
inside air/outside air changeover motor system may
be faulty.

PROBABLE CAUSES

• Malfunction of the outside/inside air selection

damper control motor

• Damaged wiring harness or connectors

• Malfunction of the heater controller assembly

(A/C-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Check the operation of the heater control
panel assembly (A/C-ECU)
Check that the A/C switch, rear window defogger
switch and air volume control dial can operate.

Q: Is the check result normal?

YES :

Go to Step 2.

NO :

INSPECTION PROCEDURE 15: Refer to
heater control panel assembly (A/C-ECU)
power supply system

P.55-28

STEP 2. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES :

Carry out the diagnosis code procedures.

Refer to

P.55-7

NO :

Go to Step 3.

STEP 3. M.U.T.-III actuator test
Carry out the actuator test. (Refer to

P.55-31

Item No.5: In/out select damper (Select
"position reset".)

Q: Does the blower motor work normally?

YES :

This diagnosis is complete.

NO :

Go to Step 4.

STEP 4. Check of open circuit in F/RA, F/RA’
F/RB and F/RB’ line between outside/inside air
selection damper control motor and heater
control panel assembly (A/C-ECU) connector.

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Repair the connector(s) or wiring harness.

STEP 5. Replace the air outside/inside air
circulation switching damper motor, and then
recheck the trouble symptom.
Check to see that the outside air/inside air circulation
switching damper motor operates normally.

NOTE: Whenever the motor is replaced, initialise the
motor position by using the Actuator Test.

Q: Is the check result normal?

YES :

This diagnosis is complete.

NO :

Replace the heater control panel assembly
(A/C-ECU).

INSPECTION PROCEDURE 6: The A/C compressor does not work

COMMENTS ON TROUBLE SYMPTOM

When the A/C compressor does not work, the A/C
compressor circuit system may be defective.

PROBABLE CAUSES

• Malfunction of the A/C compressor

• Malfunction of the A/C compressor relay

• Damaged harness wires or connectors

• Malfunction of the engine-ECU

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