GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 DeVille 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Rear of Vehicle High

Rear of Vehicle High w/F45

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 in Vehicle DTC Information

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

Is the ALC air compressor running for more than 5 minutes?

Go to Step 3

Go to Step 6

3
  1. Turn OFF the ignition.
  2. Remove the ALC compressor relay.
  3. Turn ON the ignition, with the engine OFF.

Is the air compressor running?

Go to Step 4

Go to Step 5

4
  1. Turn OFF the ignition.
  2. Reinstall the ALC compressor relay.
  3. Repair the short to voltage in the ALC air compressor control circuit.

Is the repair complete?

Go to Step 13

Go to Step 1

5
  1. Turn OFF the ignition.
  2. Replace the ALC air compressor relay.

Is the repair complete?

Go to Step 13

Go to Step 1

6

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

Are any damaged sensors or disconnected links present?

Go to Step 7

Go to Step 8

7

Replace the damaged rear position sensor or reconnect the link. Refer to Automatic Level Control Sensor Replacement .

Is the repair complete?

Go to Step 13

Go to Step 1

8
  1. Remove the ALC intake filter from the vehicle body, do not remove it from the ALC air compressor or hose.
  2. Using the scan tool, cycle ALC air compressor.
  3. After 1 minute, stop cycling.
  4. Cycle the ALC exhaust while checking to see if air is exiting the ALC intake air filter.

Is air exiting the ALC intake air filter?

Go to Step 11

Go to Step 9

9
  1. Stop exhausting.
  2. Disconnect the air tubes from both rear shock absorbers.
  3. Connect the J 22124-B ALC Pressure Gage to both (between) air tubes.
  4. Open the gage toggle valve.
  5. Disconnect the air tube from the ALC air dryer.
  6. Apply shop air to the gage schrader valve.

Is air exiting both of the air tubes at the ALC air dryer connection?

Go to Step 10

Go to Step 12

10
  1. Turn OFF the ignition.
  2. Replace the ALC air compressor assembly. Refer to Air Compressor Replacement .
  3. Install the ALC intake air filter on the vehicle body.

Are all of the replacements and/or installations complete?

Go to Step 13

--

11
  1. Turn OFF the ignition.
  2. Connect the scan tool.
  3. Turn ON the ignition, with the engine OFF.
  4. Perform the ALC relearn procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Computer/Integrating Systems.

Has the ALC relearn procedure been completed?

Go to Step 13

--

12

Replace the air tube going from the air dryer to both rear shock absorbers. Refer to Air Tube Replacement .

Is the repair complete?

a

Go to Step 13

--

13
  1. Turn OFF the ignition.
  2. Turn the ignition ON, with the engine OFF.
  3. Wait for at least 5 minutes.

Is the rear of the vehicle trim level?

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1

Rear of Vehicle High w/o F45

Step

Action

Value(s)

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 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?

0.25-2.5 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?

--

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?

--

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 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?

--

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?

--

Go to Step  10

Go to Step 7

7

Disconnect the air tube assembly from both shock absorbers.

Did the vehicle lower?

--

Go to Step  11

Go to Step 12

8

Perform the ALC relearn procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Computer/Integrating Systems.

Did you complete the procedure?

--

Go to Step 16

--

9

Inspect the 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?

--

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?

--

Go to Step 15

Go to Step 14

11

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

Did you complete the replacement?

--

Go to Step 15

--

12

Replace the shock that did not lower. Refer to Shock Absorber Replacement .

Did you complete the replacement?

--

Go to Step 15

--

13

Important : Perform the ALC relearn procedure after position sensor replacement. Refer to Body Control Module (BCM) Programming/RPO Configuration in Computer/Integrating Systems.

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

Did you complete the replacement?

--

Go to Step 15

--

14

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

Did you complete the replacement?

--

Go to Step 15

--

15

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

Does the ALC operate correctly?

--

System OK

Go to Step 2

16

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

Does the ALC operate correctly?

--

System OK

Go to Step 3