Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The temperature cannot be adjusted or the heating is insufficient.

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Recalibrate the motors. Refer to Actuator Recalibration .
4. With a scan tool, observe the current Diagnostic Trouble Code List. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Does the scan tool display DTCs?

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Go to Diagnostic System Check - Vehicle

Go to Step 3

Place the blower motor switch in each speed position.

Does the blower motor operate in any speed position?

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Go to Step 4

Go to Blower Motor Inoperative

Does the blower motor operate at the desired speeds?

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Go to Step 5

Go to Blower Motor Malfunction

1. Place the blower motor switch in the maximum speed position.
2. Place the mode controls in the bi-level position.
3. Alternately, place the recirculation switch in the outside air and recirculation positions.

Does the recirculation door move from the recirculation position to the ambient air position?

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Go to Step 6

Go to Air Recirculation Malfunction

Does the Too Cold in Vehicle concern occur when heating or defrosting is desired?

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Go to Step 7

Go to Step 9

1. Start the engine.
2. Place the HVAC control module in the OFF position.

Does the A/C compressor operate?

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Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 8

8

Inspect the cooling system for the following conditions:

Did you find and correct the condition?

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Go to Step 24

Go to Step 9

Inspect the upper and lower air temperature sensors for the following conditions:

Did you find and correct the condition?

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Go to Step 24

Go to Step 10

1. Turn ON the ignition, with the engine OFF.
2. Inspect for airflow through the inside air temperature assembly by placing a 5-cm (2-in) square piece of paper over the sensor air inlet.

Does the paper stay in place?

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Go to Step 11

Go to Step 14

1. Install a thermometer near the upper and lower air sensors and the inside air temperature assembly.
2. With a scan tool, observe the following data parameters in the HVAC Sensor data list:

•	Upper AC Duct Temp.

•	Lower Htr. Duct Temp.

•	Inside Air Temp.

For the upper and lower duct temp parameter conversion from counts to temp, refer to Sensor Resistance Table .

Does the scan tool indicate that the sensor temperatures are within the specification at the thermometer temperatures?

-3 to +3°C

(-5 to +5°F)

Go to Step 12

Go to Step 17

1. Turn the engine OFF.
2. Install a scan tool.
3. Cover the sunload sensor.
4. Start the engine.
5. Place the temperature to 22°C (72°F).
6. With a scan tool, observe the Sunload Sensor data parameter in the HVAC control module sensor data list.

Does the scan tool indicate that the sunload sensor parameter is greater than the specified value?

224 Counts

Go to Step 13

Go to Step 19

1. Uncover the sunload sensor.
2. Direct a light source at the sunload sensor.

Do the counts change?

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System OK

Go to Step 19

Test the ignition 3 voltage circuit of the HVAC control module for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 15

Test the battery positive voltage circuit of the HVAC control module for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 16

Test the ground circuit of the HVAC control module for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 20

Test the suspect temperature sensor resistance. Refer to Sensor Resistance Table .

Does the resistance measure near the Sensor Resistance Table?

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Go to Step 20

Go to Step 18

Inspect for poor connections at the harness connector of the suspect air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 21

Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 22

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

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Go to Step 24

Go to Step 23

Replace the appropriate temperature sensor. Refer to the following procedures:

Did you complete the replacement?

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Go to Step 24

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Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement .

Did you complete the replacement?

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Go to Step 24

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Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

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Go to Step 24

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3