GM Service Manual Online
For 1990-2009 cars only

Rear of Vehicle High wo/F45

Step

Action

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you review the ALC 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 sensor connector.
  2. Connect a test lamp between the battery positive voltage circuit of the ALC sensor and a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 10

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 ignition 3 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 between the automatic level control exhaust solenoid control circuit of the ALC sensor and a good ground.

Does the exhaust solenoid activate and vent air?

Go to Step 14

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 and the automatic level control exhaust solenoid control circuit of the ALC compressor.

Does the test lamp illuminate?

Go to Step 15

Go to Step 8

8

Test the automatic level control exhaust solenoid control circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 9

9

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

Did you complete the repair?

Go to Step 16

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10

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 16

--

11

Repair the open in the automatic level control sensor ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

--

12

Repair the open in the ignition 3 voltage circuit of the ALC sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

--

13

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

Did you complete the repair?

Go to Step 16

--

14

Replace the auto level control sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .

Did you complete the replacement?

Go to Step 16

--

15

Replace the auto level control air compressor head. Refer to Automatic Level Control Air Compressor Head Replacement .

Did you complete the replacement?

Go to Step 16

--

16

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3