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 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 - Automatic.
• If the blower motor operates properly in each speed position
4. Verify the scan tool parameters listed below change when pressing the appropriate switch.
* Driver Temp. Dr. Motor Command
* Psgr. Temp. Dr. Motor Command
* Recirculation Dr. Motor Command
* Mode Dr. Motor Command
• 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.
* Driver Temperature
* Passenger Temperature
* Mode
* Recirculation
• If any HVAC door does not move
Refer to DTC B0223, B022A, B0233, B023A, B0408, or B0418 HVAC - Automatic.
• If all HVAC doors move
6. Install the J43600 ACR 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 - Automatic.
• 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. Verify the scan tool parameters listed below are within 10% of ambient temperature.
* Lower Left Duct Air Temperature Sensor
* Upper Left Duct Air Temperature Sensor
* Lower Right Duct Air Temperature Sensor
* Upper Right Duct Air Temperature Sensor
* A/C Evaporator Temperature Sensor
• If not within 10% of ambient temperature
Refer to DTC B0173, B0178, B0509, B0514 or B3933 B0173.
• If within 10% of ambient temperature
10. Verify the scan tool parameters listed below are within 10% of actual conditions.
* Passenger Compartment Humidity
* Passenger Compartment Humidity Sensor Temperature
* Passenger Compartment Windshield Temperature
• If not within 10% of actual conditions
Refer to DTC B018A, B048C, B048F, or B1395 B018A.
• If within 10% of actual conditions
11. Engine ON, A/C system ON
12. Verify cool air flows from the ducts with the temperature control in the coldest position.
• If the air is not cool
1. 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 - Automatic.
• 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 - Automatic.
• If the air is cool
13. 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
14. Engine OFF, ignition ON.
15. Verify the Sunload parameter changes while covering the B10B Ambient Light/Sunload Sensor with a shop towel or other suitable item.
• If the Sunload parameter does not change
Refer to DTC B0183 B0183.
• If the Sunload parameter changes
16. Verify the actual inside air temperature, using a thermometer, is less than 3°C (5°F) difference from the scan tool Inside Passenger Compartment Air Temp. Sensor parameter.
• If greater than a 3°C (5°F) difference
Refer to DTC B0163 B0163.
• If less than a 3°C (5°F) difference
17. Verify the engine RPO code is LUK.
• If the engine RPO code is not LUK
Refer to step 19.
• If the engine RPO code is LUK
18. Verify the G17 Heater Coolant Pump turns On and Off when commanded with a scan tool.
• If the G17 Heater Coolant Pump does not turn On and Off
Refer to DTC B269A, B269C, or B269D (LUK) B269A.
• If the G17 Heater Coolant Pump does turn On and Off
19. All OK.
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.