GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2009 🢒 SLS 🢒 Suspension 🢒 Automatic Level Control 🢒 Rear of Vehicle Low

Step

Action

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn ON the ignition with the engine OFF.
  2. Listen for the automatic level control (ALC) air compressor to activate.

Does the air compressor come on within 30 seconds?

Go to Step 8

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the ALC connector from the ALC air compressor assembly.
  3. Disconnect the Electronic Suspension Module connector.
  4. Turn the ignition ON.
  5. Connect a fused jumper between the ALC relay coil supply voltage circuit and ground.
  6. Measure the voltage between the ALC compressor motor control circuit and ground.

Does the voltmeter display a voltage greater than 10 volts?

Go to Step 4

Go to Step 6

4
  1. Remove the fused jumper wire.
  2. Turn OFF the ignition.
  3. Test the ground circuit of the ALC air compressor connector for a ground.

Did you find and correct the condition?

Go to Step 13

Go to Step 5

5

Replace the ALC air compressor assembly. Refer to Air Compressor Replacement.

Is the repair complete?

Go to Step 11

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6
  1. Remove the fused jumper wire.
  2. Turn OFF the ignition.
  3. Check for the following:
    4. • Open ELC fuse
    • Bad ELC relay
    • Open circuit in ALC air compressor motor control circuit
    • Open circuit in ALC relay coil supply voltage circuit

Did you find the condition?

Go to Step 7

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7

Important: An open fuse may indicate:

    • No head relief--check for ALC codes.
    • A faulty air compressor
    • A short to ground in the exhaust solenoid battery positive circuit

Repair the short to ground in the ALC compressor battery positive circuit or replace the fuse.

Is the repair complete?

Go to Step 13

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8

Inspect the left and right rear position sensors for damage and disconnected links.

Are any damaged sensors or disconnected links present?

Go to Step 12

Go to Step 9

9

Perform the ALC System Leak Test.

Is a leak present?

Go to Step 10

Go to Step 11

10

Repair the leak in the ALC System.

Is the repair complete?

Go to Step 13

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11
  1. Turn OFF the ignition.
  2. Connect the scan tool.
  3. The ignition is ON with the engine OFF.
  4. Perform the CVRSS/ALC recalibration procedure.

Has the recalibration been completed?

Go to Step 13

--

12

Replace the damaged rear position sensor or reconnect the link.

Is the replacement complete?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2