Auto Ride Problem

[Sink1]

I recently purchased a used 2003 Denali and noticed the rear end was sagging. I thought the owner had lowered the vehicle, but when I looked underneath, I could see one of the shocks was leaking what looked like oil. I had also noticed a noise coming from the driver's side rear tire, later identified as the compressor.

 

After much research on the issue, we purchased new OEM Air Ride shocks for the rear and put them on the vehicle with no problems. It seemed to fix the sagging issue, but the compressor keeps coming on every time I turn the vehicle on/off and it seems to continue to sag after the vehicle has been parked for an extended length of time. Air Ride shocks are completely new to us, and we are not sure if it is "normal" for the compressor to come on and off so frequently, or should we replace that as well? I have observed other Yukon Denalis in parking lots when we are out and about, and they don't sag so I am guessing I still have some unresolved issue with the suspension.

 

We really love the vehicle, and want to be able to tow our boat with it, so we really need to solve this "sagging" issue. Any advice would be greatly appreciated.

 

Thanks in advance.

[superjim]

We really love the vehicle, and want to be able to tow our boat with it, so we really need to solve this "sagging" issue. Any advice would be greatly appreciated.

 

Thanks in advance.

 

 

You probably have an air leak at a fitting under the truck...between the compressor and the shocks. It could also be a tiny pinhole in one of the lines where it has rubbed on something.

 

Mix up some dishwashing liquid and water (make it REAL SOAPY) and take a small paint brush and check all of the lines and fittings for air leaks.

[Sink1]

We really love the vehicle, and want to be able to tow our boat with it, so we really need to solve this "sagging" issue. Any advice would be greatly appreciated.

 

Thanks in advance.

 

 

You probably have an air leak at a fitting under the truck...between the compressor and the shocks. It could also be a tiny pinhole in one of the lines where it has rubbed on something.

 

Mix up some dishwashing liquid and water (make it REAL SOAPY) and take a small paint brush and check all of the lines and fittings for air leaks.

 

 

 

Texas Jim-

 

Thanks for the advice. I will give that a try and I will let you know if that solves the sagging issue.

 

Since I am not familiar with these auto leveling air shocks, is that normal for me to hear the compressor go on and off as though it is conatantly "leveling" the vehicle every time I turn it on and off?

 

Thanks for the help.

[Sink1]

We really love the vehicle, and want to be able to tow our boat with it, so we really need to solve this "sagging" issue. Any advice would be greatly appreciated.

 

Thanks in advance.

 

 

You probably have an air leak at a fitting under the truck...between the compressor and the shocks. It could also be a tiny pinhole in one of the lines where it has rubbed on something.

 

Mix up some dishwashing liquid and water (make it REAL SOAPY) and take a small paint brush and check all of the lines and fittings for air leaks.

 

 

 

Texas Jim-

 

Thanks for the advice. I will give that a try and I will let you know if that solves the sagging issue.

 

Since I am not familiar with these auto leveling air shocks, is that normal for me to hear the compressor go on and off as though it is conatantly "leveling" the vehicle every time I turn it on and off?

 

Thanks for the help.

 

[superjim]

Thanks for the advice. I will give that a try and I will let you know if that solves the sagging issue.

 

Since I am not familiar with these auto leveling air shocks, is that normal for me to hear the compressor go on and off as though it is conatantly "leveling" the vehicle every time I turn it on and off?

 

Thanks for the help.

 

 

If there is a leak..then yes, it would be normal for the compressor to come on every time you start it.

It is just doing it's job and leveling everything back up.

 

If you DO NOT have a leak...then we need to explore other things, but I am betting on a small leak. They can sometimes be hard to find.

[Sink1]

Thanks for the advice. I will give that a try and I will let you know if that solves the sagging issue.

 

Since I am not familiar with these auto leveling air shocks, is that normal for me to hear the compressor go on and off as though it is conatantly "leveling" the vehicle every time I turn it on and off?

 

Thanks for the help.

 

 

If there is a leak..then yes, it would be normal for the compressor to come on every time you start it.

It is just doing it's job and leveling everything back up.

 

If you DO NOT have a leak...then we need to explore other things, but I am betting on a small leak. They can sometimes be hard to find.

 

 

Thanks again! I will attemp to check for a leak this weekend (or rather my husband will )! If that is not the problem, we'll continue to trouble shoot.

 

On a side note, after the shocks were replaced, the "Service Ride Control" message now comes up on the instrument panel, and did not prior to the shock service. Since the owner's manual explanation is hardly comprehensive, could it be possible a sensor was knocked loose when the tires were removed? I didn't think a 2003 Denali had the tire pressure sensors, but I could be wrong. Funny how this message comes on now and did not come on when there was a leak in the shock itself?

 

As always, thanks again!

[superjim]

Thanks again! I will attemp to check for a leak this weekend (or rather my husband will )! If that is not the problem, we'll continue to trouble shoot.

 

On a side note, after the shocks were replaced, the "Service Ride Control" message now comes up on the instrument panel, and did not prior to the shock service. Since the owner's manual explanation is hardly comprehensive, could it be possible a sensor was knocked loose when the tires were removed? I didn't think a 2003 Denali had the tire pressure sensors, but I could be wrong. Funny how this message comes on now and did not come on when there was a leak in the shock itself?

 

As always, thanks again!

 

 

 

OK...NOW maybe we are getting somewhere.

You didn't mention earlier that you were getting an error message about SERVICE RIDE CONTROL.

 

There are sensors attached to the suspension so that the compressor comes on and off at the appropriate time.

 

It is very possible that one of these got knocked loose or bent or wires got unplugged during the replacement of the shocks.

 

The sensors are located near the rear wheels, under the little plastic fender lining toward the front part of the inside of the fender.

It is a little rod that is attached to the suspension on one end and to a rotary device on the other end. as the suspension moves up and down, the rod pushes on the rotary device.

The rotation of the device will determine how loaded your vehicle is.

This sensor then gives the on / off command to the pump in the autoride unit.

 

There may be sensors that also plug into the shocks themselves...but I am not sure about that.

My experience with LEVEL RIDE / AUTORIDE, is limited to Cadillacs..but it should be similar.

[bernarde]

Thanks again! I will attemp to check for a leak this weekend (or rather my husband will )! If that is not the problem, we'll continue to trouble shoot.

 

On a side note, after the shocks were replaced, the "Service Ride Control" message now comes up on the instrument panel, and did not prior to the shock service. Since the owner's manual explanation is hardly comprehensive, could it be possible a sensor was knocked loose when the tires were removed? I didn't think a 2003 Denali had the tire pressure sensors, but I could be wrong. Funny how this message comes on now and did not come on when there was a leak in the shock itself?

 

As always, thanks again!

 

 

 

OK...NOW maybe we are getting somewhere.

You didn't mention earlier that you were getting an error message about SERVICE RIDE CONTROL.

 

There are sensors attached to the suspension so that the compressor comes on and off at the appropriate time.

 

It is very possible that one of these got knocked loose or bent or wires got unplugged during the replacement of the shocks.

 

The sensors are located near the rear wheels, under the little plastic fender lining toward the front part of the inside of the fender.

It is a little rod that is attached to the suspension on one end and to a rotary device on the other end. as the suspension moves up and down, the rod pushes on the rotary device.

The rotation of the device will determine how loaded your vehicle is.

This sensor then gives the on / off command to the pump in the autoride unit.

 

There may be sensors that also plug into the shocks themselves...but I am not sure about that.

My experience with LEVEL RIDE / AUTORIDE, is limited to Cadillacs..but it should be similar.

 

 

 

I have a similar problem on my 02 escalade, I have a service stability system code, and the compressor runs alot. I did remove the compressor and it is in need of replacement. would the compressor running more than it should give me the sevice code or is there more to it?

[fastestbbc]

Did anyone locate a source for the pressure switch????

[fastestbbc]

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[Tradar4213]

I have a 2002 Suburban with auto-Ride. I bought this vehicle in Feb. of this year. The compressor that levelled the vehicle worked then but recently I have not heard it kick in and when I hooked to my 10' equipment trailer the rear sagged .

I took it to the local dealer because I was not sure what fuse to check. A service tech went out to my truck and looked under the hood in the fuse box. He pointed to an empty spot and said that was my problem. It was missing a 30 amp fuse. I didn't think he was right but went along with him. The empty spot was labeled A.I.R.

He gave me a fuse and said that should solve my problem. It didn't. Am I wrong or is that fuse used only in a diesel motor?

I read the owners manual and the only fuse I could find according to it was the one marked RTD(Real Time Dampening).It was good. What else do I need to check and is there a way to check the compressor?

 

I have an 04 Tahoe LT with Autoride and recently experienced the same problem. The autoride Compressor kicked on every time I started the truck and when heavy loads or trailers were attached. It seemed like the compressor began running for longer periods of time before shutting off and then the "service autoride control" message appeared in the dash console. I read this post and there are some great helpful tips. I removed the compresssor from behind the rear driver tire and inspected the air hoses and shocks to the extent I could see/feel them. I attempted to bench test the compressor motor with a 12v battery tester and it did not turn on so I think the compressor motor is shot. I found a replacement here http://www.arnottindustries.com/part_CHEVR...d92_gid359.html. I am wondering if there is anything else wrong with the autoride system that would need to be fixed before ordering a new compressor? Other members mentioned rotary sensors near the rear wheels but I found mine located at the front of the vehicle, near the front wheels. If possible I'd like to perform a pressure test of the system. Does anyone know what pressure the autoride system operates under (psi?) or how to test the other sensors like the pressure switch attached to the dryer? It does not look like the new compressor motor comes with the dryer so I'm wondering if I could test that too? Any help would certainly be appreciated !! This site has the best inof I have found so far..thanks everyone!!

[blue dave]

Hi guys! I found this thread on Google so I joined the site to hopefully get some answers regarding the air ride system on my 2002 GMC Yukon XL Denali.

 

I replaced the complete compressor assembly (compressor, exhaust solenoid, dryer, pressure switch) as a complete unit last year and the system has worked fine until just this week.

 

I just tested the compressor by jumping 12v onto the red & black leads and it works fine. All three fuses that supply power to the entire system (IGN 3, Stud 1, & RTD) check out fine.

 

I have complete schematics of the system which show me that the red compressor wire is energized by the automatic level control relay (contact 87). The automatic level control relay (contact 30) is fed from the Stud 1 fuse under the hood. When the relay coil is energized, relay contacts 30 & 87 close to energize the red wire which feeds the compressor. The relay coil (contact 85) has + 12v supplied by a brown wire fed from fuse IGN 3 on the left side of the dash. The relay coil is energized when the other side of the coil (contact 86) receives a ground signal on the light blue wire fed from the suspension control module (connector C2 A10).

 

My problem is that do not know the location of the relay and the module. Can anybody please tell me where these two components are located?

 

 

I have one more question just out of curiosity. The orange wire fed from the RTD fuse under the hood is connected to one side of the exhaust soleniod coil. The other side of the coil is connected to a dark blue wire fed from connector C2 B5 on the suspension control module. My question is what is the purpose of the exhaust solenoid (purge water vapor?) and when does the suspension control module turn on this solenoid?

[blue dave]

OK, I found the suspension control module in the passenger side rear area behind the interior panel and under the rear HVAC blower.

 

When I ground the light blue wire on connector C2 - A10 the compressor runs which tells me that the automatic level control relay and the compressor are both working fine. I never found the relay but I guesss that it is now a moot point since it is working properly.

 

So now I need to find out why the suspension control module is not grounding the C2 - A10 output wire when it ought to be (heavy load on rear of truck). It looks like the suspension control module inputs that effect this are probably the left rear & right rear suspension position sensors (C3 - A5 & A7) and the pressure sensor (C2 - B5).

 

I now need to know how the suspension position sensors and the pressure sensor inputs effect the compressor relay output. It looks like all of the sensors use a 0-5vdc analog signal. Any help would be greatly appreciated.

[blue dave]

OK, I am making progress. As I stated above, when I force the suspension control module compressor output C2 -A10 low, the compressor runs. While it is running I can look at the rear suspension position sensor inputs and the pressure sensor input.

 

Both rear suspension position sensors are giving variable voltage inputs to the suspension control module C3 - A5 & A7 (as the vehicle ride height increases the voltage decreases). The pressure sensor also gives a variable voltage input to the suspension control module C3 - B11 (as the pressure increases so does the voltage). Therefore I am now convinced that all of these sensors are working properly.

 

Now I am looking at the suspension control module exhaust solenoid output C2 - B5. It is providing a low signal which should activate the exhaust solenoid. I confirmed that the exhaust solenoid has 12 vdc on it but the system still holds pressure (no bleed off).

 

I ohmed out the exhaust solenoid coil and it is an open circuit. It looks now like I have a bad exhaust solenoid? Perhaps the suspension control module can sense that the exhaust solenoid circuit is open and that is why it is holding that output low and will not turn on the compressor?

[blue dave]

Does anybody know if I can purchase just the exhaust solenoid. I really do not want to replace the entire compressor, exhaust solenoid, dryer, pressure switch as a complete assembly again.

 

Also out of curiosity, can anybody tell me the purpose of the exhaust solenoid and when & why it is activated?