Schematic Reference: HVAC Schematics

DEFINITION: Temperature can not be adjusted or heating insufficient.

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

Important:: The RADIO fuse must be removed for 20 seconds minimum. The HVAC control module requires 60 seconds to initialize after the Radio fuse is reinstalled. Do not install a scan tool during this time.

1. Disconnect the scan tool.
2. Turn OFF the ignition.
3. Remove the RADIO fuse to interrupt the keep alive memory of the HVAC control module.
4. Install the RADIO fuse.
5. Install a scan tool.
6. Turn ON the ignition, with the engine OFF.
7. Observe the current DTC list in Heating and Air Conditioning using the scan tool.

Does the scan tool display DTC B0229, B0414, B0434, B3761 or B3764?

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Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

Place the blower motor switch in each speed position.

Does the blower motor operate in any of the speed positions?

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Go to Step 4

Go to Blower Motor Inoperative

Does the blower motor operate at the desired speed in each speed position?

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Go to Step 5

Go to Blower Motor Malfunction

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

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Go to Step 6

Go to Step 8

1. Start the engine.
2. Place the blower motor switch in the OFF position.
3. Place the A/C request switch 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 7

Inspect the heating and cooling system for the following:

Did you find and correct the condition?

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Go to Step 24

Go to Step 8

Inspect the air temperature sensors for the following conditions:

1. An obstruction to the airflow
2. Damaged or missing seal to the sensor
3. Misaligned air ducts
4. Misaligned sensor

Refer to Air Temperature Sensor Replacement - Upper and Air Temperature Sensor Replacement - Lower .

Did you find and correct the condition?

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Go to Step 24

Go to Step 9

1. Turn ON the ignition, with the engine OFF.
2. Inspect for airflow through the inside air temperature sensor 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 10

Go to Step 13

1. Install a scan tool.
2. Cover the sunload sensor.
3. Adjust driver side temperature to 22°C (74°F).
4. With a scan tool, observe the Solar Sensor data parameter in the Primary ECC Data list.

Does the scan tool indicate that the Solar Sensor data parameter is greater than the specified value?

230 Counts

Go to Step 11

Go to Step 18

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

Do the counts change?

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Go to Step 12

Go to Step 18

1. Install a thermometer near the heater duct, A/C duct and inside air temperature sensors.
2. With a scan tool, observe the Upper Outlet Temperature, Lower Outlet Temperature and Inside Air Temp data parameters in the Primary ECC Data list.

Does the scan tool indicate the sensor temperatures are within 3°C (5°F) of the thermometer temperatures?

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System OK

Go to Step 15

Test the ignition 1 voltage circuit of the inside air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 24

Go to Step 14

Test the ground circuit of the inside air temperature sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 24

Go to Step 17

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

Did you find and correct the condition?

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Go to Step 24

Go to Step 16

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

Does the resistance measure near the Sensor Resistance Table value?

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Go to Step 19

Go to Step 20

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

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 in Wiring Systems.

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 in Wiring Systems.

Did you find and correct the condition?

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Go to Step 24

Go to Step 23

Replace the temperature sensor. Refer to Air Temperature Sensor Replacement - Upper or Air Temperature Sensor Replacement - Lower or Inside Air Temperature Sensor Replacement .

Did you complete the replacement?

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Go to Step 24

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Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement .

Did you complete the replacement?

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Go to Step 24

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Replace the sunload sensor. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

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Go to Step 24

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Important:: Perform the recalibration procedure for the HVAC control module.

Replace the HVAC Control Module. Refer to HVAC Control Module Replacement .

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 2