GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

    • The condition may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • 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 .

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

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 Status parameter in the HVAC System data list.
  2. Activate the mode switch.

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

Go to Step 6

Go to Step 7

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

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 .

Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 9

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9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2