Inspect the coolant level.

Is the coolant level correct?

Go to Step 3

Go to Step 2

Add coolant as needed.

Is the heater operating?

System OK

Go to Step 3

1. Turn the ignition to ON.
2. Observe the temperature indication screen of the controller.

Does the digit flash ON and OFF?

Go to Step 4

Go to Step 5

Perform the Diagnostic System Check - HVAC System.

Does the display indicate any error codes?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 7

Observe the blower motor operation.

Is the blower motor functioning at all?

Go to Step 6

Go to Blower Motor Inoperative

Use the blower push switch to cycle the blower through its different speeds.

Does the motor function at different speeds?

Go to Step 7

Go to DTC 6

1. Run the blower and operate the MODE push switch manually.
2. Inspect for airflow out of the various outlets.

Does the air flow from the different outlets as it should?

Step 9

Step 8

1. Remove the heater outlet and inspect for obstructions.
2. Remove any obstructions found.

Is the heater operating?

System OK

Go to Step 9

Observe the air mix door (AMD) motor while changing the temperature setting from 18-32°C (64-90°F) and then from 32-18°C (90-64°F).

Is the AMD motor functioning properly?

Go to Step 10

Go to DTC 4

Inspect the coolant hoses for leaks or kinks.

Are the coolant hoses in good condition?

Go to Step 12

Go to Step 11

Repair any problem with the coolant hoses.

Did you complete the repair?

System OK

Go to Step 12

Inspect the surge tank cap.

Is the surge tank cap in good condition?

Go to Step 14

Go to Step 13

Repair or replace the surge tank cap as needed.

Did you find and correct the condition?

System OK

Go to Step 14

1. Set the A/C switch to OFF.
2. Set the temperature control to 32°C (90°F).
3. Set the blower motor speed to FULL HIGH, all segments illuminated to the display.
4. Remove the surge tank cap.
5. Start the vehicle and run the engine at idle.
6. Watch for the flow of the coolant when the thermostat opens.

Does the coolant flow?

Go to Step 16

Go to Step 15

1. Inspect for the following conditions:

•	A faulty thermostat

•	A failed coolant pump impeller

•	A restriction in the cooling system

2. Make repairs as needed.

Did you find and correct the condition?

System OK

--

Check the temperature of the heater inlet and outlet hoses by feel.

Is the heater inlet hose hot and the outlet hose warm?

Go to Step 18

Go to Step 17

Back flush or replace the heater core.

Did you find and correct the condition?

System OK

--

Inspect the vehicle for cold air leaks at the following locations:

Where any leaks found?

Go to Step 20

Go to Step 19

Repair any cold air leaks.

Did you complete the repair?

System OK

--

Inspect the coolant temperature sensor using the tests in DTC 3 .

Is there a problem indicated in the sensor, the sensor wiring, or the controller?

Go to Step 21

Go to Step 22

Repair or replace the sensor, the wiring, or the controller as required.

Did you find and correct the condition?

System OK

--

Inspect the in-car sensor using the tests in DTC 1 .

Is there a problem indicated in the sensor, the sensor wiring, or the controller?

Go to Step 23

Go to Step 24

Repair or replace the sensor, the wiring, or the controller as required.

Did you find and correct the condition?

System OK

--

Inspect the ambient air temperature sensor using the tests in DTC 2 .

Is there a problem indicated in the sensor, the sensor wiring, or the controller?

Go to Step 25

Go to Step 26

Repair or replace the sensor, the wiring, or the controller as required.

Did you find and correct the condition?

System OK

--

Inspect the sun sensor using the tests in DTC 5 .

Is there a problem indicated in the sensor, the sensor wiring, or the controller?

Go to Step 27

Go to Step 28

Repair or replace the sensor, the wiring, or the controller as required.

Did you find and correct the condition?

System OK

--

Replace the automatic temperature control (ATC) controller.

Did you complete the replacement?

System OK

--