HVAC System Test (ATC)

*HVAC SYSTEM TEST (ATC)

For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation

The HVAC System Test provides a starting point in the diagnostic process by identifying the appropriate diagnostic procedure or system test to perform when diagnosing a given symptom, condition, or DTC. It also provides a means for testing the entire HVAC system by utilizing the A/C Heater Control's On-Board System Tests. The On-Board System Tests can also assist in diagnosing stored DTCs.

Diagnostic Test

1.HVAC SYSTEM TEST

NOTE: Diagnose and repair all active DTCs before diagnosing and repairing stored DTCs.

Make a selection based on the symptom, condition, or DTC that you want to diagnose.

For Any Active DTC

Scan Tool Indicates HVAC Not Active On Bus

- Refer to Electronic Control Modules testing for the diagnostic test procedure.

Complete HVAC System Test

- Go To 2

A/C System Performance Test

- Go To 2

General System Operation & Function Test

- Go To 3

Actuator Calibration Test

- Go To 4

2.A/C SYSTEM PERFORMANCE TEST

NOTE: The following are prerequisites of the Cooldown Test. Verify each of the following before running the test:
- If active, diagnose and repair DTC B1031 or B1032 before proceeding.

- Verify that the refrigerant system has an adequate charge. Check and repair as necessary before proceeding.
- Verify that the blower motor operates correctly in all speeds. Diagnose and repair all blower related faults before proceeding.
- Verify that the work area ambient temperature is above 18.3° C (65° F) before proceeding. Move the vehicle to a warmer work area if necessary.
- Verify that the evaporator temperature is above 18.3° C (65° F) before proceeding.
- Verify that the A/C compressor is not running. If the A/C compressor is running, turn the A/C off and allow the evaporator to warm up before proceeding.

Once all of the prerequisites have been met, actuate the Cooldown Test by performing the following:

Start the engine.

With the scan tool in HVAC, select System Tests and then select Cooldown test.

NOTE: The Cooldown Test can take up to two minutes to run. While the test is running, the A/C status indicator will flash. If the test passes, the A/C status indicator will stop flashing. However, if the test fails, both the A/C and EBL status indicators will flash alternately and an active DTC B10B2 will set. The status indicators will continue to flash until either a successful Cooldown Test is executed or until the vehicle is driven a specified number of miles or after 5 ignition cycles. In addition, DTC B10B2 will remain active until a successful Cooldown Test is executed. The test will stop running if any of the following occurs:

- The ignition is turned off.
- The A/C compressor is requested off.
- DTC B1031 or B1032 sets during the test.

Allow the test to run to completion before proceeding.

With the scan tool, select View DTCs.

Does the scan tool display any DTCs?

Yes

- Diagnose and Repair the DTC(s). Run the Cooldown Test again after the repair is complete.

No

- As necessary, either Go To 3, or 4, or Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

3.GENERAL SYSTEM OPERATION & FUNCTION TEST

NOTE: If at anytime a DTC becomes active during this test, proceed to the conclusion question.

NOTE: If multiple DTCs become active, diagnose those that relate to a short circuit first.

If not done so previously, start the engine.

Turn the blower control to manual low.

Turn the Left and Right Blend controls to full cold.

Turn the Mode control to panel.

Monitor the scan tool for active HVAC DTCs while performing the following test steps.

Press the A/C mode switch on, wait 30 seconds, press it off, and then proceed to the next step.

Press the Rear Defrost mode switch on, wait 30 seconds, press it off, and then proceed to the next step.

Press the Recirculation mode switch on, wait 30 seconds, press it off, and then proceed to the next step.

Turn the Left Blend control to full hot, wait 30 seconds, turn it to full cold, and then proceed to the next step.

Turn the Right Blend control to full hot, wait 30 seconds, turn it to full cold, and then proceed to the next step.

Turn the Mode control to every door position. Leave it in each position for 30 seconds.

Does the scan tool display any active DTCs?

Yes

- Diagnose and repair the DTC(s).

No

- If you are here due to a stored DTC, it is possible that a technician may not have erased the DTC following a repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, either Go To 4 or visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals, and repair as necessary.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

4.ACTUATOR CALIBRATION TEST

If not done so previously, start the engine.

With the scan tool, select System Tests and then select Actuator Calibration Test. When the test is complete, select View DTCs.

Does the scan tool display any DTCs?

Yes

- Diagnose and repair the DTC(s).

No

- No problem found. However, if you are here due to a stored DTC, it is possible that a technician may not have erased the DTC following a repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals, and repair as necessary.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test