GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Place the ignition switch in RUN.
  2. Depress the load leveling inflator switch ON.

The ALC compressor motor turns on and runs continuously for up to 10 minutes before shutting off.

Automatic Level Control Compressor Motor Does Not Activate

2

Depress the core of the inflator fill valve.

High pressure air is available at the inflator fill valve.

Automatic Level Control Inflator Fill Valve Inoperative

3

Depress the load leveling inflator switch OFF.

The ALC compressor motor turns off.

Automatic Level Control Compressor Motor Always On

4

Place a 250--300 lb load to the rear of the vehicle.

  1. System will have a 7--14 second delay.
  2. System will exhaust for 1 second.
  3. ALC compressor motor will turn on and raise the vehicle to a predetermined height
  4. ALC compressor will turn off.

Automatic Level Control Compressor Motor Does Not Activate

Automatic Level Control Compressor Motor Always On

Automatic Level Control Sensor Adjustment

5

Remove the load from the rear of the vehicle.

  1. System will have a 7--14 second delay.
  2. System will exhaust to a predetermined height.
  3. ALC compressor motor will turn off.

Automatic Level Control System Does Not Vent to Lower Vehicle

6

  1. Let the vehicle sit for approximately 10 minutes.
  2. The load leveling pump should not run frequently, continuously, or a maximum run time (5½ minutes).

No action from Load Leveling Pump.

Air Compressor Leak Test

7

No abnormal results were found while performing System Check.

The system is OK.

The customer complaint is not resolved. Go to Intermittents and Poor Connections Diagnosis .

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.