*HVAC SYSTEM TEST (MTC)

For a complete wiring diagram Refer to Section 8W.

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. (Refer to 24 - HEATING & AIR CONDITIONING - DIAGNOSIS AND TESTING) for additional information about on-board diagnostics.

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

Refer to the Table of Contents in this Section for a complete list of HVAC related symptoms.

Complete HVAC System Test

Go To 2

A/C System Performance Test

Go To 2

General System Operation & Function Test

Go To 3

Actuator Ckt Test / Door Cal Function

Go To 4

Blower Motor Inoperative

Refer to *Blower Motor Inoperative (MTC) in this Section.

Control Won't Display Active / Stored DTCs

Refer to *A/C Heater Control Will Not Enter Diagnostic Mode for the diagnostic test procedure.

Control Won't Run System Tests

Refer to *A/C Heater Control Will Not Enter Diagnostic Mode for the diagnostic test procedure.

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 31 or 32 before proceeding. Refer to the Table of Contents in this Section for a complete list of HVAC related symptoms.

Verify that the refrigerant system has an adequate charge. Check and repair as necessary before proceeding (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS).
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 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:

If not done so previously, start the engine.
Press and hold the A/C mode switch down and then turn the blower motor control to high speed. Continue to hold the A/C mode switch down until the A/C status indicator begins flashing, Then, release the mode switch.
NOTE: The Cooldown Test can take up to two minutes to run. While the test is running, the A/C status indicator will flash once per second. If the test passes, the A/C status indicator will stop flashing. If the test fails, the A/C and EBL status indicators will flash alternately. The test will stop running if the either ignition is turned off, or the blower control is turned to any position other than high, or if DTC 83 or 84 sets during the test.
Allow the test to run to completion before proceeding.

Actuate the Display DTC function by performing the following:

Turn the blower control on.
Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.

NOTE: The A/C Heater Control will display a DTC for every fault that it detects, not just DTCs specific to A/C performance.

NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.

Read DTCs from the A/C status indicator.

Does the A/C status indicator display any DTCs?

Yes

Diagnose and Repair the DTC(s). Refer to the Table of Contents in this Section for a complete list of HVAC related symptoms. Run the Cooldown Test again after the repair is complete.

As necessary, either Go To 3 or 4, or Perform BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

3. GENERAL SYSTEM OPERATION & FUNCTION TEST

If not done so previously, start the engine.
Turn the blower control on.
Turn the Blend control to full cold.
Turn the Mode control to panel.
Press the A/C mode switch on, wait 30 seconds, press it off, and then proceed to the next step.
Press the EBL mode switch on, wait 30 seconds, press it off, and then proceed to the next step.
Turn the 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. When complete, proceed to the next step.
Actuate the Display DTC function by performing the following:

Turn the blower control on.
Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.

NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.

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

Read DTCs from the A/C status indicator.

Does the A/C status indicator display any DTCs?

Yes

Diagnose and repair the DTC(s). Go To 4 if Overcurrent faults (DTC 41, 42, 43, and 44) are present and run the Actuator Circuit Test / Door Calibration Function. Otherwise, refer to the Table of Contents in this Section for a complete list of HVAC related symptoms.

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. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

4. ACTUATOR CIRCUIT TEST / DOOR CALIBRATION FUNCTION

NOTE: By running the Actuator Circuit Test / Door Calibration Function, the A/C Heater Control can identify up to three door driver circuits shorted simultaneously. A DTC 72 will set if more than three door driver circuits are shorted in the same direction (e.g. four door driver circuits all shorted to ground) or if two or more door driver circuits are shorted with at least one door driver circuit shorted to ignition and one door driver circuit shorted to ground. To ensure a proper diagnosis, diagnose and repair Actuator Circuit Test faults in the following order: If present, diagnose and repair DTC 72 first, then DTC 62, then DTC 61, then DTCs 64, 66, 68, or 71, and finally DTCs 63, 65, 67, or 69. In addition, always test the door driver circuits after each repair by clearing DTCs, and then running the Actuator Circuit Test / Door Calibration Function, and then checking for DTCs.

NOTE: Diagnose and repair Actuator Circuit Test faults (DTC 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, and 72) before diagnosing Overcurrent faults (DTC 41, 42, 43, and 44) and Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56). Diagnose and repair Overcurrent faults (DTC 41, 42, 43, and 44) before diagnosing Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56).

If not done so previously, turn the ignition on.
Actuate the Clear DTC function by performing the following:

Turn the blower control on.
Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.
When the A/C status indicator begins flashing DTCs, set the Mode switch to the floor position, simultaneously press the A/C mode switch and the EBL mode switch down until both LEDs start flashing (approximately 5 seconds) and then release the mode switches. Stored DTCs will clear from memory in approximately two seconds. However, if no DTCs were present, both status indicators will turn off and the system will exit diagnostic mode.

Turn the ignition off, wait 10 seconds, and turn the ignition on.
Actuate the Actuator Circuit Test / Door Calibration Function by performing the following:

Turn the blower control off.
Press and hold the EBL mode switch down and then turn the blower control on. Continue to hold the EBL mode switch down until the EBL status indicator begins flashing. Then, release the EBL mode switch. While the test / function is running, the EBL status indicator will flash once per second. If the test / function passes, the EBL status indicator will stop flashing. If the test / function fails, the A/C and EBL status indicators will flash alternately. Allow the test / function to run to completion before proceeding.

Actuate the Display DTC function by performing the following:

Turn the blower control on.
Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.

NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.

Read DTCs from the A/C status indicator.

Does the A/C status indicator display any DTCs?

Yes

Diagnose and repair the DTC(s). Refer to the Table of Contents in this Section for a complete list of HVAC related symptoms.

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. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).