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 Electrical Diagrams

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Description and Operation

Manual HVAC Description and Operation HVAC - Manual

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 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 DTC B0193 B0193.

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 B0223.

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 (LFX, LS3, L99) Air Conditioning (A/C) System Performance TestAir Conditioning (A/C) System Performance Test (LSA) Air Conditioning (A/C) System Performance Test.

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

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

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* HVAC Component Replacement Reference Removal and Replacement

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