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 - Manual
Connector End View Reference
Component Connector End Views Sunshade - Left
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
Special Tools
J43600 - ACR Air Conditioning Service Center
Circuit/System Verification
Note: Check for bulletins before proceeding.
1. Ignition ON.
2. Verify the scan tool Blower Motor Switch parameter changes when rotating the blower switch through each speed position.
• If the parameter does not change for each speed position
Replace the A26 HVAC Controls.
• If the parameter changes for each speed position
3. Verify the blower motor operates properly with the blower motor switch in each speed position.
• If the blower motor does not operate in each speed position
Refer to DTC B0193 HVAC - Manual
• If the blower motor operates properly in each speed position
4. Verify the scan tool parameters listed below change when pressing the appropriate switch.
* Left Temperature Knob Position
* Air Recirculation Mode Switch
* Bi-Level Switch
• If any parameter does not change
Replace the A26 HVAC Controls
• If all parameters change
5. Verify the HVAC doors listed below move when pressing the appropriate switch.
* Temperature
* Bi-Level mode
* Recirculation
• If any HVAC door does not move
Refer to DTC B0223, B0233, B023A, or B0408 HVAC - Manual
• If all HVAC doors move
6. Install the J43600 - Air Conditioning Service Center.
7. Verify the high side pressure reading on the Air Conditioning Service Center is within 10% of the scan tool A/C High Side Pressure Sensor parameter.
• If the reading is not within 10%
Refer to DTC P0532 or P0533 HVAC - Manual
• If the reading is within 10%
8. Verify the A/C High Side Pressure Sensor parameter is between 269-2929 kPa (39-425 PSI).
• If the reading is not between 269-2929 kPa (39-425 PSI)
Refer to Air Conditioning (A/C) System Performance Test Air Conditioning (A/C) System Performance Test.
• If the reading is between 269-2929 kPa (39-425 PSI)
9. Engine ON, A/C system ON.
10. Verify cool air flows from the ducts with the temperature control in the coldest position.
• If the air is not cool
1. Observe the Q2 A/C Compressor Clutch.
2. Verify the Q2 A/C Compressor Clutch is engaged.
• If the Q2 A/C Compressor Clutch is not engaged
Refer to DTC P0645, P0646, or P0647 HVAC - Manual.
• If the Q2 A/C Compressor Clutch is engaged
Refer to Air Conditioning (A/C) System Performance Test Air Conditioning (A/C) System Performance Test and DTC B393B HVAC - Manual.
• If the air is cool
11. Verify warm air flows from the ducts with the temperature control in the warmest position.
• If the air is not warm
Refer to Heating Performance Diagnostic Heating Performance Diagnostic.
• If the air is warm
12. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* HVAC Component Replacement Reference HVAC Component Replacement Reference
* Control Module References Control Module References for HVAC control module replacement, programming, and setup.