GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the automatic level control suspension system operation and perform the necessary inspections?

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Go to Step 2

Go to Symptoms

2

Verify that the ALC compressor motor is always on.

Does the ALC system operate normally?

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

Go to Step 3

3

  1. Turn the ignition switch to the RUN position. Do not start the engine.
  2. Disconnect the ALC timer relay.

Does the ALC air compressor pump stop running?

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Go to Step 4

Go to Step 9

4

Test CKT 1250 (BLK) at terminal F, of the ALC timer relay for a short to ground.

Is a short to ground present in CKT 1250 (BLK)?

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Go to Step 5

Go to Step 8

5

  1. Disconnect the ALC inflator air switch.
  2. Test CKT 1250 (BLK) at terminal F of the ALC timer relay for a short to ground.

Is a short to ground present in CKT 1250 (BLK)?

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Go to Step 6

Go to Step 7

6

Repair the short to ground in CKT 1250 (BLK). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

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Go to Step 16

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7

Replace the ALC inflator air switch. Refer to Automatic Level Control Inflator Air Switch Replacement .

Is the replacement complete?

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Go to Step 16

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8

Replace the ALC timer relay. Refer to Automatic Level Control Relay Replacement .

Is the replacement complete?

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Go to Step 16

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9

Disconnect the ALC sensor.

Does the ALC Air Compressor pump stop running?

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Go to Step 10

Go to Step 11

10

Replace the ALC sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .

Is the replacement complete?

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Go to Step 16

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11

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the ALC Air Compressor.
  3. Test CKT 321 (YEL) of the ALC Air Compressor for a short to ground.

Is a short to ground present in CKT 321 (YEL)

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Go to Step 12

Go to Step 13

12

Repair the short to ground in CKT 321 (YEL). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

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Go to Step 16

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13

  1. Remove the relay in the ALC Air Compressor.
  2. Reconnect the ALC Air Compressor pump.

Does the ALC Air Compressor pump run?

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Go to Step 14

Go to Step 15

14

Repair the short to voltage on the BLK/LT GRN wire. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

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Go to Step 16

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15

Replace the relay in the ALC Air Compressor. Refer to Air Compressor Relay Replacement .

Is the replacement complete?

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Go to Step 16

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16

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3