For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: Component Connector End Views
1 |

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 2

Go to Step 3

2 | Perform the Diagnostic System Check - HVAC Systems - Automatic . Does the display indicate any error codes? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 7
3 | Observe the blower motor operation. Is the blower motor functioning at all? | Go to Step 4 | Go to Blower Motor Inoperative
4 | Use the blower push switch to cycle the blower through its different speeds. Does the motor function at different speeds? | Go to Step 5 | Go to Diagnostic Trouble Code (DTC) List and use DTC 6.
5 |

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?

Go to Step 7

Go to Step 6

6 |

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

Is the heater operating?

System OK

Go to Step 9

7 | 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 8 | Go to Diagnostic Trouble Code (DTC) List and use DTC 3.
8 | Perform the checks found in HVAC Preliminary Checks . Is the system operating normally now? | System OK | Go to Step 9
9 | Place the controller in the AUTO mode. Is any air taken into the intake port of the in-car sensor? | Go to Step 12 | Go to Step 10
10 | Inspect the intake hose for the in-car sensor. Is the hose in good condition? | Go to Step 12 | Go to Step 11
11 | Repair or replace the intake hose. Did you find and correct the condition? | System OK | --
12 | Inspect the in-car sensor using the tests in DTC 1. Refer to Diagnostic Trouble Code (DTC) List . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 13 | Go to Step 14
13 | Repair or replace the sensor, the wiring, or the controller as required. Did you find and correct the condition? | System OK | --
14 | Inspect the ambient air temperature sensor using the tests in DTC 2. Refer to Diagnostic Trouble Code (DTC) List . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 15 | Go to Step 16
15 | Repair or replace the sensor, the wiring, or the controller, as required. Did you find and correct the condition? | System OK | --
16 | Inspect the sun sensor using the tests in DTC 5. Refer to Diagnostic Trouble Code (DTC) List . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 17 | Go to Step 18
17 | Repair or replace the sensor, the wiring, or the controller as required. Did you find and correct the condition? | System OK | --
18 | Perform the coolant temperature sensor test. Is the coolant temperature sensor malfunctioning? | Go to Step 19 | Go to Step 20
19 | Replace the coolant temperature sensor. Did you complete the replacement? | System OK | --
20 | Replace the automatic temperature control (ATC) controller. Did you complete the replacement? | System OK | --