Pressurizing air shocks……

[Doubeleive]

Finally got around to replacing the compressor. Runs much quieter now so don’t mind that I replaced it. Same issue still persists though. I command the pump on and it pressurizes the shocks. I drive around and turn the car off. Next time I go to the car the shocks are totally deflated and the pump won’t turn on. The SCM won’t give command to air up(I can only inflate them with the scanner command, the SCM won’t do it by itself). If there was a leak I’d assume the SCM would just keep pumping them up? I also checked the height sensor. It’s 0.33v when shocks are deflated and 1.7v when they are inflated. This is right from the SCM module. So the SCM SW can read it.
shocks flat = 37 1/8” height @ 0.33V
Shocks inflated = 38 1/8” height @ 1.7v

I’m thinking that I need my SCM programmed to my VIN? I just replaced the SCM but it just had a generic looking SW load in there. Not sure if it’s even controlling anything I just can com with it and command it to do certain functions….

Do you think that’s my next logical step here?

you might have a couple things going on
1. the shocks should hold air, even if they sit for weeks, so there is "likely" a leak some where, use some soap and water mix in a sprayer and start spraying all over when fully inflated. be patient and keep spraying until you find the bubbles, this includes spraying the new pump and relief valve. you won't hurt anything spraying it, it's water tight or should be.
2. there could be a module communication issue still, I would check the harness over real good it is exposed to the elements so any corrosion and dirt etc should be cleaned up, try some contact cleaner like crc contact cleaner.
as for pumping the shocks up when the air leaks out No I did not find this to be the case, the system is kind of dumb in that respect, it will or should pump up if there is a load applied but if the air leaks out after just driving around it did not for me until I cycled the key.
otherwise mine always did as commanded with the scanner, never had any communication problems

I don't think the system monitors the air pressure 24/7 while driving, which is why people are able to get away with deleting the system and just adding resistors
i also think it only pumps up the system when the ride height sensors change ohm's, and it's a set it and forget it type of thing (just speculation)
you could try leaving it running until the shocks have depleted some and then add a load, a trailer or have a couple people stand on the bumper and see if it detects a load and inflates the system again. (theoretically it should) but might not.

 

[ReaperHWK]

you might have a couple things going on
1. the shocks should hold air, even if they sit for weeks, so there is "likely" a leak some where, use some soap and water mix in a sprayer and start spraying all over when fully inflated. be patient and keep spraying until you find the bubbles, this includes spraying the new pump and relief valve. you won't hurt anything spraying it, it's water tight or should be.
2. there could be a module communication issue still, I would check the harness over real good it is exposed to the elements so any corrosion and dirt etc should be cleaned up, try some contact cleaner like crc contact cleaner.
as for pumping the shocks up when the air leaks out No I did not find this to be the case, the system is kind of dumb in that respect, it will or should pump up if there is a load applied but if the air leaks out after just driving around it did not for me until I cycled the key.
otherwise mine always did as commanded with the scanner, never had any communication problems

I don't think the system monitors the air pressure 24/7 while driving, which is why people are able to get away with deleting the system and just adding resistors
i also think it only pumps up the system when the ride height sensors change ohm's, and it's a set it and forget it type of thing (just speculation)
you could try leaving it running until the shocks have depleted some and then add a load, a trailer or have a couple people stand on the bumper and see if it detects a load and inflates the system again. (theoretically it should) but might not.

Thanks for that. It’s going to the dealer next Friday for the SCM load though. I just want to make sure I have a good firmware load and then I’ll check for all these leaks.

 

[Big Mama]

Like Wes said. I don’t think your shocks should empty when you park. The only scenario I can think of that let’s air out of the shock is after they aired up due to a load, you remove the load and they lower. The compressor should kick on with each ignition cycle for a few seconds but it sounds like yours stays on much longer bbIs it possible there’s a leak and you don’t hear the new compressor running more than it should? Wes, do I have this right? If so is there another scenario where shocks deflate? If so, what/where does the air exit?

 

[Joseph Garcia]

I believe that the SCM needs to be programmed for your truck's VIN, so if you replaced it, get it programmed.

 

[Doubeleive]

Like Wes said. I don’t think your shocks should empty when you park. The only scenario I can think of that let’s air out of the shock is after they aired up due to a load, you remove the load and they lower. The compressor should kick on with each ignition cycle for a few seconds but it sounds like yours stays on much longer bbIs it possible there’s a leak and you don’t hear the new compressor running more than it should? Wes, do I have this right? If so is there another scenario where shocks deflate? If so, what/where does the air exit?

The pump only runs for a max amount of time I forget how many seconds 30? maybe presuming there is a bad leak and it can't fill the shocks, because it is for intermittent use only, not designed to run constantly or it will just burn out.
even with a load sitting on it, the shocks should hold air for a extended period of time, when the load is removed then it sense's the ride height has risen so it opens the relief valve on the pump and lets some air out.

from my testing it appeared that the "normal/average" unloaded psi is around 20-25, it should be around that same psi even days later if it has sat parked with no key cycle
when the key is cycled, usually (but not always per gm for unexplained reasons) it should release a small amount of the stored air sounds like a short "woosh" from the relief valve, it does this to ease the pressure on the pump when it kicks on, then it should come on for a few seconds pressurizing to 20-25 and then again there will be a very short "woosh" right as the pump shuts off. then it should hold air at that level presuming there are no leaks and no load added.
if it leaks it just leaks and proceeds to ride like a Ford, yes I said it those things handle like a boat on the water. no pressure in the shocks so if you do a lane change you will feel the rear end sway unusually. I could feel the difference with just a 10psi drop

 

[ReaperHWK]

Sitting here at the dealer just got it programmed. Service manager comes out and said the module took the program but now the SCM is reporting several codes with a list of errors…..
I even have the dash saying “leveling system error” which is a good thing because I know the shocks are flat. Looks like the SCM is smart now.

Probably a good thing. I’ll scan it when I get home. Hopefully will point me to the root issue.

I also notice now both shocks are pumped up. Looks like the SCM is commanding the compressors on. I’m excited lol.

So bottom line is that a new OEM SCM will come with a base program so it can comm with the computers and modules as well as do basic test functions but it is not programmed to control the suspension and monitor for faults. Need to get it programmed for sure.

Hopefully I’ll have time this weekend to work on it more. I’ll post up the codes and what I find.

 

[Big Mama]

Thanks for closing the loop for the next guy.

 

[ReaperHWK]

The pump only runs for a max amount of time I forget how many seconds 30? maybe presuming there is a bad leak and it can't fill the shocks, because it is for intermittent use only, not designed to run constantly or it will just burn out.
even with a load sitting on it, the shocks should hold air for a extended period of time, when the load is removed then it sense's the ride height has risen so it opens the relief valve on the pump and lets some air out.

from my testing it appeared that the "normal/average" unloaded psi is around 20-25, it should be around that same psi even days later if it has sat parked with no key cycle
when the key is cycled, usually (but not always per gm for unexplained reasons) it should release a small amount of the stored air sounds like a short "woosh" from the relief valve, it does this to ease the pressure on the pump when it kicks on, then it should come on for a few seconds pressurizing to 20-25 and then again there will be a very short "woosh" right as the pump shuts off. then it should hold air at that level presuming there are no leaks and no load added.
if it leaks it just leaks and proceeds to ride like a Ford, yes I said it those things handle like a boat on the water. no pressure in the shocks so if you do a lane change you will feel the rear end sway unusually. I could feel the difference with just a 10psi drop

So no I was mistaken the air shocks aren’t pumping up but I do have a code for it(my scanner says the level control is disabled because of an error which is the c0660:05 below). Looks like the exhaust solenoid isn’t communicating. I have a new entire compressor assembly installed as well. Also have comm faults for 3 out of the 4 shocks. Here is a screenshot of my codes now from the SCM. Looks like it’s all “open” codes so there is a broken wire or disconnected harness I’m assuming?

 

[Doubeleive]

So no I was mistaken the air shocks aren’t pumping up but I do have a code for it(my scanner says the level control is disabled because of an error which is the c0660:05 below). Looks like the exhaust solenoid isn’t communicating. I have a new entire compressor assembly installed as well. Also have comm faults for 3 out of the 4 shocks. Here is a screenshot of my codes now from the SCM. Looks like it’s all “open” codes so there is a broken wire or disconnected harness I’m assuming?

View attachment 437950

are the front shocks the original? do they have the electrical plug on the top of the shaft? are they BWI? or aftermarket?

 

[ReaperHWK]

are the front shocks the original? do they have the electrical plug on the top of the shaft? are they BWI? or aftermarket?

All oem as far as I know. I bought the truck with 100k miles about 6 years ago and it has 150k miles now. I’ll check all the connectors on the shocks.

Worked fine for 50k miles until the SCM shorted out by wire harness rubbing on the frame. I’ll have to check the wires again maybe I missed some……