GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for blower motor operation in the off setting.

  1. This step test for blower motor operation in any speed setting.

  1. This step test for proper blower motor speed in each setting.

  1. This step test for proper operation of the recirculation actuator.

  1. This step checks for an internal fault in the HVAC control module.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Air does not flow correctly from the air distribution outlets.

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. Turn OFF the HVAC controls.

Is the blower motor OFF?

Go to Step 3

Go to Blower Motor Always On

3

Place the blower motor control in each speed position.

Does the blower motor operate at all?

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor operate correctly in each speed position?

Go to Step 5

Go to Blower Motor Malfunction

5
  1. Place the blower motor control in the maximum speed position.
  2. Place the mode controls in the bi-level position.
  3. Alternately place recirculation switch in the outside air and recirculation positions.

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

Go to Step 6

Go to Air Recirculation Malfunction

6
  1. Install a scan tool.
  2. Select the display DTCs function for the HVAC Control Module.

Does the scan tool display any DTCs?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 7

7

Place the mode controls in each mode position.

Does the air flow from the correct air distribution outlets for each selected mode position?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 8

8
  1. With the scan tool, observe the Selected Air Mode parameter in the HVAC Control Module data list.
  2. Place the mode controls in each mode position.

Does the scan tool display the correct state for each selected mode?

Go to Step 10

Go to Step 9

9

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 12

Go to Step 11

10
  1. Inspect and the air distribution system for the following:
    2. • A restricted passenger compartment air filter.
    • An obstruction restricting air flow.
    • Air leaks.
    • Misaligned ducts.
  2. Perform any necessary repairs.

Did you complete the repair?

Go to Step 12

--

11

Important: Perform the recalibration procedure for the HVAC control module.

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

Did you complete the replacement?

Go to Step 12

--

12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3