DEFINITION: The automatic level control (ALC) compressor operates (runs), but the system exhibits the one or more of the following conditions:

Did you perform the ALC diagnostic system check?

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Go to Step 2

Go to Automatic Level Control System Operation Check

1. Inspect the entire ALC system for disconnected or damaged ALC system hoses or connectors. Repair or replace the components as necessary.
2. Turn the ignition OFF.
3. Disconnect the air hose from one of the rear shock absorbers.
4. Connect the J 22124-B between the shock absorber and the shock absorber air hose.
5. Open the J 22124-B toggle valve (up position).

Important: 

•	The trim height sensor MUST be adjusted properly.

•	The vehicle MUST be supported by the suspension.

•	The vehicle rear MUST be loaded with approximately 181 kg (400 lb).

6. Turn the ignition ON.
7. Apply service air pressure to the J 22124-B service valve until the J 22124-B gauge shows the specified value.

Do both of the rear corners of the vehicle rise?

759 kPa (110 psi)

Go to Step 3

Go to Step 17

Observe the J 22124-B gauge for 1 minute.

Important: After one minute, the pressure may fall TO the specified value. This is acceptable.

Does the system pressure drop BELOW the specified value?

620 kPa (90 psi)

Go to Step 4

Go to Step 10

1. Remove the air filter hose end from the underbody
2. Apply service air pressure to the J 22124-B service valve until the J 22124-B gauge shows the specified value.

Do you hear air pressure escaping through the air filter hose?

759 kPa (110 psi)

Go to Step 5

Go to Step 9

1. Disconnect the compressor electrical connector.
2. Connect a test light between the compressor electrical connector terminals B and C.

Is the test light on?

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Go to Step 6

Go to Step 8

1. Disconnect the trim height sensor electrical connector.
2. Inspect CKT 320 for a short to ground.
3. Repair the short as necessary.

Does the customer concern still exist?

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Go to Step 7

System OK

If CKT 320 is not shorted, replace the trim height sensor. Refer to Automatic Level Control Sensor Replacement .

Does the customer concern still exist?

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Go to Automatic Level Control System Operation Check

System OK

The vent solenoid valve is stuck open. Replace the compressor head. Refer to Automatic Level Control Air Compressor Head Replacement .

Does the customer concern still exist?

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Go to Automatic Level Control System Operation Check

System OK

1. Apply service air pressure to the J 22124-B service valve until the J 22124-B gauge shows the specified value.
2. Use a stethoscope (if available) in order to inspect the ALC system for AUDIBLE indications of air pressure leak(s) and/or apply a soap and water solution to all of the ALC system components in order to inspect the ALC system for VISUAL indications of air pressure leak(s). Inspect the following components:

•	The air hoses

•	The compressor

•	The shock absorbers

•	The inflator solenoid

3. Repair or replace the leaking component(s) as necessary.

Does the customer concern still exist?

759 kPa (110 psi)

Go to Automatic Level Control System Operation Check

System OK

1. With the ALC system holding air pressure, disconnect the air hose from the air dryer.
2. Inspect the J 22124-B gauge.

Does the rear of the vehicle lower and the air pressure escape?

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Go to Step 12

Go to Step 11

1. Inspect the inflator solenoid (if applicable) and the air hoses between the shock absorbers and the compressor for any air path restrictions.
2. Repair or replace the components as necessary.

Does the customer concern still exist?

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Go to Automatic Level Control System Operation Check

System OK

1. Connect the air hose to the air dryer.
2. Disconnect the compressor electrical connector.
3. Using fused jumpers, connect the ALC compressor electrical connector terminals A and E to B+, and connect terminals D and G to ground.
4. Allow the compressor to run until the J 22124-B gauge shows the specified value.

Does the compressor develop the specified system pressure?

759 kPa (110 psi)

Intermittent Condition

Go to Automatic Level Control System Operation Check

Go to Step 13

1. Disconnect the fused jumper from terminal E in order to stop the compressor motor.
2. Disconnect the air filter hose (compressor inlet) from the air compressor.
3. Connect the fused jumper to terminal E in order to allow the compressor motor to run.

Does the compressor now develop the specified system pressure?

759 kPa (110 psi)

Go to Step 14

Go to Step 15

Replace the air filter hose. Refer to Automatic Level Control Air Filter Hose Replacement .

Does the customer concern still exist?

Go to Automatic Level Control System Operation Check

System OK

1. Disconnect the fused jumper from terminal E in order to stop the compressor motor.
2. Remove the air dryer and install a known good air dryer to the compressor. Refer to Automatic Level Control Air Dryer Replacement .
3. Connect the fused jumper to terminal E in order to allow the compressor motor to run.

Does the compressor now develop the specified system pressure?

759 kPa (110 psi)

System OK

Go to Step 16

Replace the compressor. Refer to Air Compressor Replacement .

Does the customer concern still exist?

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Go to Automatic Level Control System Operation Check

System OK

1. Inspect the air hoses between the shock absorbers and the compressor for restrictions and leaks.
2. If the air hoses are in good condition, replace the shock absorber(s) that did not inflate. Refer to Shock Absorber Replacement in Rear Suspension.

Does the customer concern still exist?

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Go to Automatic Level Control System Operation Check

System OK