GM Service Manual Online
For 1990-2009 cars only

Improper Air Delivery or No Mode Shift

Step

Action

Yes

No

1

Perform the function test. Refer to Function Test .

Did you find the air delivery incorrect?

Go to Step 2

System OK

2

Inspect the affected valve actuator for the following conditions:

    • Correct vacuum hose installation
    • Proper linkage connection

Are the installations and connections correct?

Go to Step 4

Go to Step 3

3

Reinstall the valve actuator or repair the connections as needed. Refer to Vacuum Hose Harness Replacement .

Does the condition persist?

Go to Step 4

System OK

4

  1. Disconnect the actuator from the valve.
  2. Inspect the valve for the following conditions:
  3. • Proper travel
    • Proper effort
    • Spring correctly installed

Is the valve operating properly?

Go to Step 6

Go to Step 5

5

Repair the valve as needed.

Does the condition persist?

Go to Step 6

System OK

6

  1. Remove the control assembly from the dash. Refer to Control Assembly Replacement .
  2. Inspect the violet vacuum hose for engine manifold vacuum while the engine is operating.

Is the vacuum present?

Go to Step 7

Go to Step 8

7

Using a hand vacuum pump test each vacuum hose to the actuators and the actuators for leaks? Did you find and repair the condition?

System OK

Go to Step 9

8

Inspect for vacuum source to the vacuum tank.

Did you complete the repair?

System OK

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9

Replace the control assembly.

Did you complete the repair?

System OK

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