HVAC System Malfunction

HVAC System Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Aids

Check the following mechanical fault sources:

* Air distribution box

* Air distribution hoses/air distribution ducts

Reference Information

Schematic Reference

HVAC Schematics HVAC - Automatic

Connector End View Reference

Component Connector End Views Sunshade - Left

Description and Operation

Automatic HVAC Description and Operation HVAC - Automatic

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Programming and Relearning

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 DTC B0193 HVAC - Automatic.

2. Using the scan tool observe the mode, temperature, air inlet 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 B0223, B0233, B023A, or B0408 HVAC - Automatic.

3. Engine ON, A/C ON, place the temperature control in the coldest position. Verify that cool air flows from the ducts in the vehicle.

• If the air is not cool, refer to Air Conditioning (A/C) System Performance Test 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 Sunload Sensor parameter changes.

• If it does not change, refer to Circuit/System Testing DTC B0183 B0183.

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

• If not within the specified range, refer to Circuit/System Testing DTC B0163 B0163.

7. Ignition ON, observe the scan tool A/C Evaporator Temperature Sensor parameter. The reading should be between -39°F (-35°C) and 185°F (85°C) and change with evaporator air temperature changes.

• If not within the specified range, refer to Circuit/System Testing DTC B0173, B0178, or B3933 B0173.

Repair Instructions

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

* HVAC Component Replacement Reference Removal and Replacement

* Control Module References Programming and Relearning for HVAC control module replacement, setup, and programming