09 Escalade Rear Air Suspension

[BAWLin in WI]

My rear suspension isn't functioning properly, and it's starting to drive me nuts.

I have owned the Escalade for a few months and previous owner had converted the fronts to traditional suspension and also replace rear compressors. I noticed the first time i towed something a few weeks ago the back end was sagging pretty hard. I checked all the fuses (I think) that are linked to the air suspension and they were all fine.

Now I have no idea what to check to see why the rear isn't activating. So I'm hoping I can find an answer as to what to check next.

Thanks

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[Costal_Cat]

when you start up the truck you should hear the compressor do a self-check. If this is not occurring then you probably have a bad compressor. When you were putting your trailer on the truck as the back end went down do you hear the compressor kick on? What happens is the rear gets weight and that causes the leveling sensor to move so that triggers the compressor to put air in the shocks. When it gets level from the air shocks raising the vehicle it cuts off. When you remove the load the sensor will trigger that the vehicle is sitting too high and will release air.


If you have no codes or messages your troubleshooting steps should be

1. Check that compressor is doing a self-check during startup
2. Add weight to the back, this doesn't have to be a trailer just get in the back or have your kids and a cooler in there and it should trigger the above sequence
3. If the above occurs and the compressor is constantly running or runs every few minutes then your shocks are leaking or bladder is blown.
4. If the compressor never kicks in and you checked the fuse and relay then start with a new compressor.

If you have to replace the compressor and shocks you can make the decision to go with passive and retain the air leveling functionality to save some money. Otherwise, you can go to a traditional suspension but you will need to replace the springs.

There are a lot of threads that go through your replacement options but the above steps should help you determine what you are dealing with.

Cheers,

 

[97audia4]

when you start up the truck you should hear the compressor do a self-check. If this is not occurring then you probably have a bad compressor. When you were putting your trailer on the truck as the back end went down do you hear the compressor kick on? What happens is the rear gets weight and that causes the leveling sensor to move so that triggers the compressor to put air in the shocks. When it gets level from the air shocks raising the vehicle it cuts off. When you remove the load the sensor will trigger that the vehicle is sitting too high and will release air.


If you have no codes or messages your troubleshooting steps should be

1. Check that compressor is doing a self-check during startup
2. Add weight to the back, this doesn't have to be a trailer just get in the back or have your kids and a cooler in there and it should trigger the above sequence
3. If the above occurs and the compressor is constantly running or runs every few minutes then your shocks are leaking or bladder is blown.
4. If the compressor never kicks in and you checked the fuse and relay then start with a new compressor.

If you have to replace the compressor and shocks you can make the decision to go with passive and retain the air leveling functionality to save some money. Otherwise, you can go to a traditional suspension but you will need to replace the springs.

There are a lot of threads that go through your replacement options but the above steps should help you determine what you are dealing with.

Cheers,

I have never had my compressor kick on at Al when starting , even when towing it didn't say or activate . I have no codes for suspension but I'd like to activate the compressor to make sure it is working .

 

[Costal_Cat]

I have never had my compressor kick on at Al when starting , even when towing it didn't say or activate . I have no codes for suspension but I'd like to activate the compressor to make sure it is working .

Here is what should happen

"The system also performs a self test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds then monitors the position sensor’s signal voltage inputs to verify the compressor is functioning and the system is holding air pressure."

There is a trim set recalibration that can be done but you need a Tech 2 scan tool to do that.

You can jump the connection at the relay under the hood to see if the compressor comes on. You should jump 30 to 87 on the ALC Relay Socket. Pretty simple with a piece of wire. You should also check the fuse

YouTube video here

When I replaced mine it started doing this self-test but did not before.

 

[SlickA70]

My Z55 EXT was lowered in garbage lowering springs with blown shocks at all 4 corners. I ended up replacing everything with all factory equipment and brought it back up to factory height and it rode okay.

I read about the ALC Trimset recalibration and took it to my dealer and for $90 it dialed all the new suspension in and I have to say it feels like a Cadillac again.

Very impressed in how much of a difference the process made, just wanted to give my 2 cents for anyone who maybe having issues with ride quality.

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[Zero8 Yukon]

when you start up the truck you should hear the compressor do a self-check. If this is not occurring then you probably have a bad compressor. When you were putting your trailer on the truck as the back end went down do you hear the compressor kick on? What happens is the rear gets weight and that causes the leveling sensor to move so that triggers the compressor to put air in the shocks. When it gets level from the air shocks raising the vehicle it cuts off. When you remove the load the sensor will trigger that the vehicle is sitting too high and will release air.


If you have no codes or messages your troubleshooting steps should be

1. Check that compressor is doing a self-check during startup
2. Add weight to the back, this doesn't have to be a trailer just get in the back or have your kids and a cooler in there and it should trigger the above sequence
3. If the above occurs and the compressor is constantly running or runs every few minutes then your shocks are leaking or bladder is blown.
4. If the compressor never kicks in and you checked the fuse and relay then start with a new compressor.

If you have to replace the compressor and shocks you can make the decision to go with passive and retain the air leveling functionality to save some money. Otherwise, you can go to a traditional suspension but you will need to replace the springs.

There are a lot of threads that go through your replacement options but the above steps should help you determine what you are dealing with.

Cheers,

I have a 2008 Yukon Denali. I'm not getting the self-check. I've jumped 30 to 87 and my compressor runs. I'm certain i need shocks because they look like they've been to the sun and back. Would bad shocks negate the self-check?

 

[wjburken]

I have a 2008 Yukon Denali. I'm not getting the self-check. I've jumped 30 to 87 and my compressor runs. I'm certain i need shocks because they look like they've been to the sun and back. Would bad shocks negate the self-check?

I don't think bad shocks would negate the self check. They would more likely cause the compressor to burn up if they are leaking and it keeps trying to inflate them to level the vehicle. You may have a bad Air Suspension Compressor Relay. If you load up the rear of the Yukon do you hear the compressor kick on? In reading various posts on here, I think it is about 50/50 for those that here their compressor kick on momentarily at start-up versus those that don't. I don't hear mine all the time and my wife who drives it usually doesn't even pay attention to it.

If you replace the rear shocks, and I would if they look as bad as you say, or have 100K on them, I would go with Arnott AS-2700's (new) or AS-2708's (rebuilt).

Here is a picture of where the relay is located.

 

[petethepug]

The first thing that pops into mind is the truck mentioned is running traditional suspension w/ OE bags in back. I never knew that could be done. If you have level sensors up front and they’re disabled, wouldn’t the rear sensors be confused?


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[wjburken]

The first thing that pops is the truck is running traditional suspension w/ OE bags in back. I never knew that could be done. If you have level sensors up front and they’re disabled, wouldn’t the rear sensors be confused?


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Are you referring to the front height sensors or the connection on the shock for ride control? There are two separate systems. Auto Ride Control that has a harness that plugs into the actual shock and Auto Level Control which is a separate angle position sensor that is mounted to the frame and is rotated up or down by a rod attached to the control arm.

 

[petethepug]

... previous owner had converted the fronts to traditional suspension and also replace rear compressors. I noticed the first time i towed something a few weeks ago the back end was sagging pretty hard.

The back end sagging could be excessive tongue weight, rear bags blown / disabled or both. Figure that just one portion of the the BCM controlled suspension is bypassed, whatever’s left of the Z55 /Z95 system is compromised.


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