Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The auxiliary air temperature cannot be adjusted from one or both auxiliary controls, or the auxiliary 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 in Vehicle DTC Information

The auxiliary HVAC control module cannot request A/C compressor operation. An A/C request must be generated by the HVAC control module to provide cooled airflow through the auxiliary system.

Does the HVAC control module operate and provide sufficient heating?

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Go to Step 3

Go to Too Cold in Vehicle

3

1. Install a scan tool.
2. Recalibrate the motors. Refer to Actuator Recalibration .
3. Turn ON the ignition, with the engine OFF.
4. Observe the current DTC list in Instrument Panel Module using the scan tool.

Does the scan tool display DTC B0428 or B0429?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 4

Place the auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate in each speed position?

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Go to Step 5

Go to Auxiliary Blower Motor Inoperative

Does the auxiliary blower operate at the desired speed?

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Go to Step 6

Go to Auxiliary Blower Motor Malfunction

Does the Too Cold In Vehicle concern occur when heat is desired?

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Go to Step 7

Go to Step 8

Perform the Heating Performance Diagnostic test. Refer to Heating Performance Diagnostic .

Did you find and correct the condition?

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Go to Step 19

Go to Step 8

1. Place the auxiliary air temperature switch from the coldest position to the hottest position.
2. Observe the Rear Temp. offset parameter in the Rear Climate Control Panel.

Does the scan tool indicate that the value of the Rear Temp. offset parameter changes from the minimum specified value to the maximum specified value?

-4 to 4

Go to Step 9

Go to Step 13

1. Observe the Rear Temp Dr. Actual parameter in the Instrument Panel Module.
2. Place the left air temperature switch of the front HVAC control module from the coldest position to the warmest position.

Does the scan tool indicate that the value of the Rear Temp Dr. Actual parameter changes from the minimum specified value to the maximum specified value?

0-255 counts

Go to Step 10

Go to Step 15

Inspect the auxiliary air temperature sensor for the following conditions:

Did you find and correct the condition?

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Go to Step 19

Go to Step 11

1. Install a thermometer near the auxiliary air temperature sensor.
2. With a scan tool, observe the Rear Duct Temp data parameters in the Instrument Panel Module HVAC Sensors Data list.

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

-3 to 3°C

(-5 to 5°F)

Go to Step 19

Go to Step 12

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

Does the resistance measure near the Sensor Resistance Table value?

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Go to Step 16

Go to Step 14

Inspect for poor connections at the harness connector of the auxiliary 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 19

Go to Step 17

Inspect for poor connections at the harness connector of the auxiliary 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 19

Go to Step 16

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 19

Go to Step 18

Replace the auxiliary air temperature sensor. Refer to Air Temperature Sensor Replacement - Auxiliary .

Did you complete the replacement?

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Go to Step 19

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Replace the auxiliary HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

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Go to Step 19

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Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

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Go to Step 19

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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