GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper

Diagnostic Aids
    • The condition may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • Ensure that the panel vents are in the OPEN position for proper diagnosis.
    • Inspect the air delivery system for the following conditions:
       - An obstruction to the airflow
       - Air leaks
       - Misaligned air ducts
       - Broken or binding linkages or doors
    • If the scan tool indicates that the Door Actual parameter is 5-10 counts from the Commanded Door parameter, then perform the recalibration procedure for the HVAC door actuators. Refer to Actuator Recalibration .
    • Recirc will only operate for approximately 10 minutes when selected. After 10 minutes the recirc door switches to the outside air position. The tone of the blower and the velocity of the air speed may be noticeably different when the recirc actuator switches positions. This is a normal condition. If excessive air speed change is noticed inspect the cabin air filter for contamination or blockage.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the blower motor switch in the OFF position.

Is the blower motor OFF?

Go to Step 3

Go to Blower Motor Always On

3

Place the blower motor switch in each speed position.

Does the blower motor operate in any of the speed positions?

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor operate in each speed position?

Go to Step 5

Go to Blower Motor Malfunction

5
  1. With a scan tool, observe the Mode Switch parameter in the Heating and Air Conditioning data list.
  2. Activate the mode switch.

Does the scan tool indicate that the Mode Switch parameter changes state?

Go to Step 6

Go to Step 8

6
  1. Place the blower motor switch in the maximum speed position.
  2. Place the mode switch in the bi-level position.
  3. Place the recirculation switch in the ON position.
  4. Observe the drive shaft of the recirculation actuator.
  5. Place the recirculation switch in the OFF position.

Does the recirculation door move from the recirculation position to the outside air position?

Go to Step 7

Go to Air Recirculation Malfunction

7
  1. Place the mode switch in the floor position.
  2. Turn ON the auxiliary HVAC control module.
  3. Place the auxiliary mode switch in the vent position.
  4. Observe the airflow from the auxiliary outlets.
  5. Place the front mode switch in the defrost position.

Does air flow from the auxiliary outlets?

Go to Air Delivery Improper - Auxiliary

Go to Diagnostic Aids

8

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

9

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

Go to Step 10

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10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2