GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With the scan tool, observe the suspension position sensor in the rear integration module (RIM).

Does the scan tool indicate that the suspension position sensor is within the specified range?

0.25-3.0 V

Go to Step 8

Go to Step 3

3

With the scan tool command the exhaust solenoid open to vent the system. An audible hiss sound may be heard.

Did the automatic level control (ALC) system vent and the vehicle lower?

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Go to Step 4

Go to Step 6

4

Observe the suspension position sensor reading on the scan tool.

Did the suspension position sensor reading change more than 1 volt?

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Go to Step 8

Go to Step 5

5

Important: The vehicle must be raised on a drive on lift. Full vehicle weight must be on the rear tires. Care must be used when disconnecting and retaining the suspension position sensor link. If the link is allowed to travel freely, a false DTC may be set.

  1. Disconnect the suspension position sensor actuating link.
  2. Move the position sensor link up so that it is approximately 45 degrees above the level to the floor and retain it there.
  3. With a scan tool, observe the suspension position sensor parameter.

Did the suspension position sensor reading change more than 1 volt?

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Go to Step 8

Go to Step 9

6

Important: The vehicle must be raised on a drive on lift. Full vehicle weight must be on the rear tires.

  1. Raise and support the vehicle.
  2. Disconnect the air tube assembly from the drier.

Did the ALC system vent and the vehicle lower?

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Go to Step  10

Go to Step 7

7

Disconnect the air tube assembly from both shock absorbers.

Did the vehicle lower?

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Go to Step  11

Go to Step 12

8

Perform the ALC relearn procedure. Refer to Control Module References in Computer/Integrating Systems.

Did you complete the procedure?

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Go to Step 16

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9

Inspect for poor connections/terminal tension at the harness connector of the suspension position sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 15

Go to Step 13

10

Inspect for poor connections/terminal tension at the harness connector of the automatic level control compressor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 15

Go to Step 14

11

Replace the air tube assembly. Refer to Air Tube Replacement .

Did you complete the replacement?

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Go to Step 15

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12

Replace the shock that did not lower.

Did you complete the replacement?

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Go to Step 15

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13

Important: Perform the ALC relearn procedure after position sensor replacement.

Replace the suspension position sensor. Refer to Automatic Level Control Sensor Replacement .

Did you complete the replacement?

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Go to Step 15

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14

Replace the automatic level control compressor head assembly. Refer to Air Compressor Replacement .

Did you complete the replacement?

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Go to Step 15

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15

Operate the vehicle within the conditions for enabling the automatic level control.

Does the ALC operate correctly?

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System OK

Go to Step 2

16

Operate the vehicle within the conditions for enabling the automatic level control.

Does the ALC operate correctly?

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System OK

Go to Step 3