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Air Temperature Malfunction




Air Temperature Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Reference Information
Schematic Reference

HVAC Schematics (HVAC - Automatic) HVAC Schematics HVAC Schematics
Connector End View Reference

Component Connector End Views (Connector Views) Component Connector End ViewsComponent Connector End Views
Description and Operation

* Air Delivery Description and Operation (Air Delivery) Air Delivery Description and OperationAir Delivery Description and Operation
* Air Temperature Description and Operation (Air Temperature) Air Temperature Description and Operation Air Temperature Description and Operation

Electrical Information Reference

* Circuit Testing (Circuit Testing) Circuit Testing Circuit Testing
* Connector Repairs (Connector Repairs) Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections) Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs (Wiring Repairs) Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References (Programming and Relearning) Control Module References Control Module References for scan tool information

Circuit/System Verification

Note: Check for bulletins before proceeding.

1. Ignition ON, place the blower motor switch in each speed position. Verify that the blower motor operates properly in each position.

• If the blower motor does not operate properly in all speeds, refer to Blower Motor Malfunction (Blower Motor Malfunction).

2. Using the scan tool observe the mode, temperature and recirculation door positions. Verify the actual and commanded door positions are within 4 counts of each other.

• If not within the specified range, refer to Circuit/System Testing DTC B0228, B0413, B0423, or B3779 (HVAC - Automatic)

3. Engine ON, A/C ON, place the temperature control in the coldest position. Verify that the A/C compressor clutch engages.

• If the A/C compressor compressor clutch does not engage, refer to Air Conditioning Compressor Malfunction (Air Conditioning Compressor Malfunction)
• If the A/C compressor is engaged, but air is insufficiently cooled. Refer to Air Conditioning (A/C) System Performance Test (Diesel Engine) (Initial Inspection and Diagnostic Overview)Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) (Initial Inspection and Diagnostic Overview)Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) (Initial Inspection and Diagnostic Overview)Air Conditioning (A/C) System Performance Test (HP2) (Initial Inspection and Diagnostic Overview).

4. Turn the A/C OFF and place the temperature control in the warmest position.

• If the air is insufficiently heated refer to Heating Performance Diagnostic (Heating Performance Diagnostic).

5. Engine OFF, ignition ON, cover the sunload sensor assembly with a shop towel or other suitable item. Verify the scan tool Right Sunload Sensor and Left Sunload Sensor parameters are within 3 counts of each other.

• If not within the specified range, refer to Sun Load Sensor Circuit Malfunction.

6. Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Outside Air Temp. Raw parameter. The measured temperature should be within 5 degrees of parameter.

• If not within the specified range, refer to Ambient Air Temperature Sensor Circuit Malfunction.

7. Measure actual inside air temperature using a thermometer. Compare this value to the scan tool Inside Air Temp. Sensor parameter and Aux. Inside Air Temp. parameter. The measured temperature should be within 5 degrees of parameter.

• If not within the specified range, refer to Inside Air Temperature Sensor Circuit Malfunction.

8. Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5 degrees of appropriate Duct Actual parameter.

• If not within the specified range, refer to Duct Temperature Sensor Circuit Malfunction.

9. Ignition ON, observe the scan tool A/C Evaporator Temperature Sensor parameter. The reading should be between -39°F (-35°C) and 208°F (98°C) and change with evaporator air temperature changes.

• If not within the specified range, refer to Evaporator Air Temperature Sensor Circuit Malfunction.

Circuit/System Testing

Sun Load Sensor Circuit Malfunction

Important: If a solar load sensor has an out of range condition caused by a short to voltage, short to ground, or an open/high resistance, the scan tool will display the same value: 225 counts.


1. Ignition OFF, disconnect the harness connector at the sunload sensor.
2. Test for less than 10 ohms between the ground circuit terminal C and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below:

* Left solar load sensor circuit terminal A.
* Right solar load sensor circuit terminal B.

• If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. If all circuits test normal, test or replace the sunload sensor.

Ambient Air Temperature Sensor Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the ambient temperature sensor.
2. Test for less than 10 ohms between the low reference circuit terminal B and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, verify the scan tool Outside Air Temp. Raw parameter is greater than 85°C (185°F).

• If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.

4. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Outside Air Temp. Raw parameter is less than -35°C (-39°F).

• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. If all circuits test normal, test or replace the ambient temperature sensor.

Inside Air Temperature Sensor Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate inside air temperature sensor.
2. Test for less than 10 ohms between the ground circuit terminal C and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates between the control circuit terminal B and ground.

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.

4. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal D and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. Ignition ON, verify the appropriate scan tool Inside Temp Sensor parameter is greater than 85°C (185°F).

• If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.

6. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Temp Sensor Voltage parameter is less than -35°C (-39°F).

• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

7. If all circuits test normal, test or replace the appropriate temperature sensor.

Duct Temperature Sensor Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Test for less than 10 ohms between the low reference circuit terminal A and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, verify the appropriate Duct Temp Sensor Actual parameter is greater than 85°C (185°F).

• If less than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the HVAC control module.

4. Install a 3-amp fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool Duct Temp Sensor Actual parameter is less than -35°C (-39°F).

• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. If all circuits test normal, test or replace the appropriate temperature sensor.

Important: If the evaporator air temperature sensor has an out of range condition caused by a short to voltage, short to ground, or an open/high resistance, the scan tool will display the same value: 11°C (51°F).


Evaporator Air Temperature Sensor Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the evaporator air temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and low reference circuit terminal 2.

• If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. If all circuits test normal, test or replace the evaporator air temperature sensor.

Component Testing

1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Test for the appropriate resistance between the signal terminal A or 1 and the low reference terminal B or 2. Refer to Sensor Resistance Table (Electrical Specifications) for resistance values.

If not within the specified range, replace the appropriate sensor.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) Diagnostic Repair Verification Diagnostic Repair Verification after completing the diagnostic procedure.

* Duct Air Temperature Sensor Replacement - Lower Left Side (Duct Air Temperature Sensor Replacement - Lower Left Side) Duct Air Temperature Sensor Replacement - Lower Left Side Duct Air Temperature Sensor Replacement - Lower Left Side
* Duct Air Temperature Sensor Replacement - Lower Right Side (Duct Air Temperature Sensor Replacement - Lower Right Side) Duct Air Temperature Sensor Replacement - Lower Right
Side Duct Air Temperature Sensor Replacement - Lower Right Side
* Duct Air Temperature Sensor Replacement - Upper Left Side (Duct Air Temperature Sensor Replacement - Upper Left Side) Duct Air Temperature Sensor Replacement - Upper Left SideDuct Air Temperature Sensor Replacement - Upper Right Side
* Duct Air Temperature Sensor Replacement - Lower Left Side (Duct Air Temperature Sensor Replacement - Lower Left Side) Duct Air Temperature Sensor Replacement - Lower Left SideDuct Air Temperature Sensor Replacement - Upper Left Side
* Air Conditioning Refrigerant Temperature Sensor Replacement (HVAC - Automatic) Air Conditioning Refrigerant Temperature Sensor Replacement
* Ambient Air Temperature Sensor Replacement (Service and Repair) Ambient Air Temperature Sensor Replacement
* Ambient Light Sensor Replacement (Service and Repair) Ambient Light Sensor Replacement
* Control Module References (Programming and Relearning) Control Module
References Control Module References

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