Load leveler malfunction

[carl425]

For some reason the rear end on my '99 STS is raised all the way up and won't come down. What would cause this? It looks like an old school muscle car right now, riding around all jacked up in back. I checked and neither of the sensors in back are disconnected or popped off their mounts or anything like that. It's not giving me any codes either. Is there any way to release the air in the strut and start over from "scratch"? Any help with this is appreciated.

[micahdaniel]

I'd be curious to see pics of that action

[JimD]

Pull the air line of one of the shocks to release the air pressure.

Sounds like the compressor exhaust valve is not working properly. Should set a code.

[Jeff Wilson]

I had the exact same problem the solution was to replace the LR ride height sensor.

[growe3]

There should be a suspension code set.

Check the ride height compressor fuses. I think they are in the trunk fuse block.

Check ALL of the fuses, there is a compressor fuse and suspension fuses. Replace

as necessary with the correct fuse size/rating.

You can release the air shocks by removing the air supply line then put it back on.

Note that when the air is released, the car will come down quickly. You do not

want to be caught in a "pinch point"! (Hand, arm or head crushed)

While you can reach up and do it with the car on the ground, it is safer to place

a jack under a body point, to prevent the sudden lowering.

After the air is discharged, the air line put back on, rotate lock clips to lock position, and then lower the jack.

When you turn the key to the ON position, the compressor should start and apply a small amount

of air pressure, about 7 PSI as a pre-load condition; this is normal.

To release the air shocks lock clips, see attached image. Note this is for a 1993, yours should be similar.

-George

[carl425]

Yup, George worked like a champ! Thanks for the detailed info and diagram. I unfortunately don't have a report on the cause for the failure as I checked all the fuses and they were all good. I let the air out as described and then drove the car again and the problem didn't come back. Hopefully I'm lucky enough for it to have been a one-time occurrence...

[growe3]

Glad to hear it helped.

With all of the electronic controls, it is a wonder how good these systems work; normally with few problems.

-George

[WarrenJ]

Here's some info from your FSM you might find interesting.

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Automatic Level Control System Operation with Road Sensing Suspension

Raising the Vehicle

When a load is added to the vehicle, the vehicle body moves down causing the position sensors actuating arms to rotate upward. The upward arm movements activates an internal timing circuit and, after an initial fixed delay, the CVRSS control module provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the shock absorbers through the air tubes.

As the shock absorbers inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1.0 in), the compressor relay circuit is opened and the compressor is turned off.

Air Compressor Head Relief Sequence

In order to reduce current draw during air compressor starting, the CVRSS control module performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows:

1. Exhaust solenoid is energized.

2. Air compressor is activated 1.3 seconds after the exhaust solenoid is energized.

3. Exhaust solenoid is de-energized 0.5 seconds after the air compressor is activated.

Lowering the Vehicle

When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit. After the initial fixed delay, the CVRSS control module provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the shock absorbers, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1.0 in), the exhaust solenoid circuit is opened, which closes the exhaust solenoid and prevents air from escaping.

Air Replenishment Cycle

An air replenishment cycle (ARC) is commanded after each ignition-ON cycle. The purpose of the ARC is to ensure that the ALC system is operating at or above minimum air pressure (residual air pressure). The ARC occurs as follows:

1. The EXHAUST SOLENOID IS ENERGIZED 20 seconds after the ignition has been turned on.

2. The AIR COMPRESSOR IS ACTIVATED 1.3 seconds after the exhaust solenoid is energized.

3. The EXHAUST SOLENOID IS DE-ENERGIZED 0.5 seconds after the air compressor is activated.

4. The AIR COMPRESSOR IS DEACTIVATED 3.2 seconds after the exhaust solenoid is de-energized.

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Document ID# 304391

1999 Cadillac Seville