2006 Envoy Denali Air Suspension OEM

Jkb242

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May 19, 2019
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Just noticed two signs of an apparent suspension issue.

*Car appears to be noticeably low in the rear
*When turning on the ignition key not hearing the air pump run to charge the shocks as it always has done in the past.

The air compressor access in the rear, for inflating recreational devices, runs when pressing the switch. The pressure measured at the sherader valve is >60psi (dial gauge measures up to 60 psi full scale).

Thanks to Mooseman for the service manual, it was possible for me to determine that fuse #1 or #48 feeds the compressor and the switch but it doesn’t show the detailed compressor switching. Which fused circuit feeds the switch and which one the pump uses for low shock pressure. I presume they are are separate. The actuators and fused feeds simply are tied to switching that isn’t shown in the schematic. I imagine one fuse may feed the compressor drive when the shock actuators go low and the other fuse feeds the circuit that is switched on when the inflator port is used. Without a lift, it doesn’t seem to be reasonable to pay an hourly rate to have someone else troubleshoot what I could do myself “if I only had a lift”. (Kind of like the straw man in the Wizard of Oz)

At this point, I’m wondering if replacing the shocks with say a Monroe or equivalent, NOT air shocks, so I would like some input as to a suitable replacement? Not sure it’s safe to be driving even locally around town with the shocks apparently deflated.

Any additional troubleshooting suggested?

Thanks!
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,199
Brighton, CO
Its not shocks... They are Air Springs. They are still available from Arnott, and a few others.

Or you could always just delete the air system, replace the Air Springs with Springs, and replace the shocks for shocks that are designed for Spring Rate Suspension.

I prefer the Air Springs, I think they ride better, but are known to be problematic, and rather expensive to fix.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
I vote to replace with regular springs. Sure the air ride is nice but damned expensive to fix. Sounds more like your compressor has quit and that's expensive, even more than the bags themselves. Hence why the majority of people go for.the regular springs.
 

Jkb242

Original poster
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May 19, 2019
250
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I vote to replace with regular springs. Sure the air ride is nice but damned expensive to fix. Sounds more like your compressor has quit and that's expensive, even more than the bags themselves. Hence why the majority of people go for.the regular springs.
The compressor works as explained since I can switch it on in the rear cargo area for inflating things.

So given that, I would like to know if there is a control board separate from the compressor itself? If so, is it serviceable meaning can it be reached without a lift? My 2002 SLT had conventional springs with shocks and it rode soooo great. I would like to be sure I have not overlooked something that could be a simple fix before ripping the air springs out and going with springs and new shocks. Thanks
 

Jkb242

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May 19, 2019
250
CLT
Its not shocks... They are Air Springs. They are still available from Arnott, and a few others.

Or you could always just delete the air system, replace the Air Springs with Springs, and replace the shocks for shocks that are designed for Spring Rate Suspension.

I prefer the Air Springs, I think they ride better, but are known to be problematic, and rather expensive to fix.
Thanks for the info and the correction for the proper name of the springs. If the compressor was running but not keeping the proper pressure, then there is assurance that part of the system is working. Replacing the air springs doesn’t seem to be the end of this issue. Please recall that the compressor is working when operating the rear cargo switch.

This suggests a common circuit issue exist. I don’t have a write up of how a low or improper level is detected to turn on the compressor. It seems unlikely both actuators are bad. There has to be some feed back to the control circuit to start the compressor and when to turn it off. Since the compressor isn’t operating, except when the rear cargo switch is actuated, it doesn’t seem to me the compressor or the air springs are at fault. Do you know if there is a description of this circuit I could read?

any information would be very much appreciated.

Thanks
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,199
Brighton, CO
Not entirely true. If this just recently started happening, and the air suspension WAS working correctly, and now it has developed a leak, to which the Air Compressor can no longer keep up on, it will turn off the compressor after so long, and try again at a latter point, or next key cycle.

Another possibility is that the suspension arm sensor is faulty, or even disconnected. So it cant tell that its sitting to low/high, and that it either needs to turn on the compressor/vent air.

Your process for diagnosis is going to be finding out if the air compressor does still work in providing the air bags air, or if its even being commanded to be turned on by the air ride level sensor.
 
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northcreek

Member
Jan 15, 2012
3,346
WNY
There is no serviceable circuitry, the compressor unit contains the brains of the whole system. The only real adjustment that you can make are the actuators.
Some have had luck servicing the check valve on the compressor which is the only serviceable part.
So assuming that your actuators aren’t damaged it’s either the bags or compressor which are both remove and replace items or go the spring route as others have suggested.
 
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Jkb242

Original poster
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May 19, 2019
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Thanks for the replies.

I posted a reply yesterday regarding troubleshooting the air springs being inoperative and hoping for a reply as described in that post. Since the compressor operates as explained, I know it isn’t defective. Given the cost of a conversion or repair of the current system by a shop, I wanted to properly diagnose the real issue to see if their might be a simple fix to the current problem.

Additionally, I would appreciate confirmation that this system is not monitored by the body computer or ECM. Unlike the new ride control systems that came later. Is this simply an unmonitored rear air spring application that if replaced with springs and shocks would not require any bypass or programming to prevent codes or warnings. I would like to understand exactly what is involved in this exchange before going in that direction.
Please advise.

Much thanks
 

Jkb242

Original poster
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May 19, 2019
250
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Not entirely true. If this just recently started happening, and the air suspension WAS working correctly, and now it has developed a leak, to which the Air Compressor can no longer keep up on, it will turn off the compressor after so long, and try again at a latter point, or next key cycle.

Another possibility is that the suspension arm sensor is faulty, or even disconnected. So it cant tell that its sitting to low/high, and that it either needs to turn on the compressor/vent air.

Your process for diagnosis is going to be finding out if the air compressor does still work in providing the air bags air, or if its even being commanded to be turned on by the air ride level sensor.

I did not see any replies this morning before the message I just posted. Thanks indeed. As stated the compressor is running just not being turned on automatically by the system. Switching it on with the rear cargo switch starts it running. Ignition key on after a day or so after sitting doesn’t trigger the compressor. From the info provided in the replies it seem completely actuator related since it seems that is the only thing keeping it from turning on.
leaving the vehicle low in the rear.
I’m going to a shop with a lift Friday to do a sanity check on what I cannot see at this point. At that time I will see if the actuator linkage could be moved slightly to trigger the compressor and look for any damage or connection issues.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
It is totally independent and will not throw a code or light. I'd be looking at the level sensors.

Just because the compressor turns on manually, it may still be bad . There is a valve that will send the air either to the bags or to the inflator. If something ain't right with the valve or circuit that controls it, it may not allow the compressor to operate as you wouldn't want air at the inflator if nothing is hooked up to it. You would need a schematic of the compressor itself which likely doesn't exist.
 
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Jkb242

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May 19, 2019
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I had thought there would likely be no codes but glad you confirmed it. I agree the actuators are suspect.

There must also be a valve that diverts air to the rear cargo aux air fitting when inflating things to prevent air going to the air springs. Otherwise, operating the rear cargo switch would inflate the Air springs as well which is not the case.

I also must believe if the compressor is replace, (it is available aftermarket) the diverted valve and the control circuits from the actuators would not be included in that kit.

Thank you very much.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,199
Brighton, CO
GM designed them to be all in one self contained units. I would have to believe the diverter valve is included. Do I know that for sure? No.

That said, a replacement compressor for these trucks is.. well expensive. Ranging from 400 up to 2000 new. Most would agree that a used compressor is suspect.. at best.
 

Jkb242

Original poster
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May 19, 2019
250
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It is totally independent and will not throw a code or light. I'd be looking at the level sensors.

Just because the compressor turns on manually, it may still be bad . There is a valve that will send the air either to the bags or to the inflator. If something ain't right with the valve or circuit that controls it, it may not allow the compressor to operate as you wouldn't want air at the inflator if nothing is hooked up to it. You would need a schematic of the compressor itself which likely doesn't exist.
I believe you are correct, a drawing showing the actual connections of the the valves and the mechanical/electrical controls is not available as you stated. For me, the information here has been most beneficial and I’m grateful to all who responded. At this point when the vehicle goes on the lift, if moving the actuators, whatever amount might be possible, doesn’t turn on the compressor, I’m replacing with conventional shocks and springs recommended if available. By the way Arnott no longer sells direct to DIY’ers only to their distributors.
 
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Jkb242

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May 19, 2019
250
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GM designed them to be all in one self contained units. I would have to believe the diverter valve is included. Do I know that for sure? No.

That said, a replacement compressor for these trucks is.. well expensive. Ranging from 400 up to 2000 new. Most would agree that a used compressor is suspect.. at best.
Holy cow, that much? You’re correct, it’s a no brainer if the GM part is the only way to get the entire package.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,199
Brighton, CO
Holy cow, that much? You’re correct, it’s a no brainer if the GM part is the only way to get the entire package.
I believe you get the entire package from the aftermarket sources as well..

And those are the Aftermarket prices.

The compressor assembly from GM.. Well its no longer available.

First 2 items listed.
 

Jkb242

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May 19, 2019
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Hi guys, it appears my hunch was correct. The problem with the compressor not running to level the rear of the vehicle was the left rear sensor. It broke where the plastic arm ties into the threaded adjustable linkage Once on the car was on the lift it was easy to spot. Unfortunately, it wasn’t possible to keep the arm in the correct position while holding it by hand but the compressor ran for a few seconds while it was in the correct position. I presume the two sensors have to be close to the same position to start that the compressor. the shop was doing this to help diagnose this for free so I couldn’t ask them to remove and inspect the broken sensor.

I think it makes sense to get a replacement actuator to see if this corrects the issue since we know the compressor is working normally. Did anyone know if these are still available as a OEM part? Nervous about using Dorman.
 
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Mooseman

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Dec 4, 2011
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Ottawa, ON
Should be available. Check online places like gmpartsdirect to see if it lists a price or says NLA. Also check RA.
 
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Jkb242

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May 19, 2019
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Of course, just didn’t register. I called them too, they had nothing related to any parts for this year model. I found two new actuators (likely dreaded Dorman) on EBay for $90 for the pair Guaranteed F/F. Likely the best I can do. The labor to install these plus the parts, needs to be at reasonable price point to gamble this will fix the issue and avoid the cost of the Spring kit.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
Labour should be cheap, maybe 10 minutes per side. Very easy and accessible to replace. It's the adjustment afterwards that could take some time as you have to measure side to side and front to back and adjust each sensor accordingly, lather, rinse, repeat.
 

Jkb242

Original poster
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May 19, 2019
250
CLT
Should be available. Check online places like gmpartsdirect to see if it lists a price or says NLA. Also check RA.
UPDATE…
Raised the vehicle today to make certain that only the actuator was broken. I’m going to order an actuator that someone has posted an OEM replacement on EBay. I presume this came from an actual GM application.

Any adjustments or calibration required after he actuator is replaced?

It’s no longer sitting low but appears to be slightly higher than normal. The air springs apparently actuated about a week ago on their on perhaps sometime after I moved the broken actuator when I discovered this. Today, I measured the length of the right side actuator linkage which is not broken to make certain that length is matches the replacement left side actuator.

Much thanks again.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
You'll have to adjust the level sensors to the proper ride height. These trucks usually ride with a slight forward take but if you don't like that, you can certainly lower the rear. Also check for side to side.
 

Jkb242

Original poster
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May 19, 2019
250
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Some kind responder to this thread posted or referenced a TBS for servicing/adjusting the level sensors which I wanted to read thoroughly before replacing the broken sensor. I cannot find that TBS or the reply that contained it.
The Dorman sensors seem to be the only replacements available. RA has none. My intention therefore is to replace the broken driver side check for level side to side as suggested then see if the air springs adjust at next fill up which they always have. If the air springs operation return to normal I may replace the other sensor. Would this be valid to confirm proper operation?

From the pictures of the replacement Dorman sensors I have found, none appear to have any means for adjustment. No apparent threaded connecting arm, just appears to be a solid piece? Seems odd.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
Through some Goodle-fu, I found this thread:


And within that thread found the TSB # 06-03-09-006B which brought me here:


However, info in there is minimal, actually quite unhelpful, as it just says to adjust according to SI.

If you want to read some more, we do have a few threads on the subject:

 

Jkb242

Original poster
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May 19, 2019
250
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You killed this one for me mooseman. This is exactly the info I had seen. Reviewing now. It also occurred to me that the darn adjustment of the sensors is movement of the entire sensor within the slots of the sensor body not any sort of threaded rod? Wel, that’s how it appears from the posts. Interesting indeed. Guess I’ll have to play around with the decal as two procedures were mentioned. Measurement of the receiver hitch height instead of the fender height is nice for comparison. MUCH THANKS AGAIN!!
 
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