GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you review the Automatic Level Control System Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Automatic Level Control

2

  1. Disconnect the auto level control (ALC) sensor connector.
  2. Connect a test lamp between battery positive voltage circuit of the ALC sensor and a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 14

3

Connect a test lamp between the battery positive voltage circuit and the ground circuit of the ALC sensor.

Does the test lamp illuminate?

Go to Step 4

Go to Step 11

4

  1. Turn ON the ignition, with the engine OFF.
  2. Connect a test lamp between the accessory voltage circuit of the ALC sensor and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 12

5

Connect a 10 A fused jumper wire between the ALC exhaust solenoid control circuit of the ALC sensor and a good ground.

Does the exhaust solenoid activate and vent air?

Go to Step 15

Go to Step 6

6

Inspect the fuse in the jumper wire.

Did the fuse in the jumper open?

Go to Step 13

Go to Step 7

7

  1. Leave the 10 A fused jumper connected.
  2. Disconnect the ALC air compressor connector.
  3. Connect a test lamp between the battery positive voltage circuit of the ALC air compressor connector and ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 9

8

Connect a test lamp between the battery positive voltage circuit and the exhaust signal circuit of the ALC air compressor connector.

Does the test lamp illuminate?

Go to Step 16

Go to Step 10

9

Repair the open in the battery positive voltage circuit of the ALC air compressor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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10

Repair the open in the ALC exhaust solenoid control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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11

Repair the open in the ground circuit of the ALC sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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12

Repair the open in the accessory voltage circuit of the ALC sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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13

Repair the short to voltage in the ALC exhaust solenoid control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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14

Repair the open in the battery positive voltage circuit of the ALC sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

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15

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

Did you complete the replacement?

Go to Step 17

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16

Replace the ALC air compressor head. Refer to Automatic Level Control Air Compressor Head Replacement .

Did you complete the replacement?

Go to Step 17

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17

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3