Pressurizing air shocks……

2015 Tahoe LTZ

I just replaced my suspension controller and repaired some wires. Some wires shorted and blew out the controller. Fixed wires and installed new controller all the errors went away and the computer can talk to the suspension controller(BCM and my scanner now). I can also do active tests and see that all the data is good between every shock and the controller. Looks like I’m back in business!


However all the shocks are totally flat; my scanner has a function to pressurize the system but it’s not clear (to me). I assume I do this procedure and then do the shock level initialization my scanner also has? Here is a screen shot of the scanner for the pressurization before it starts.



Do I just let all 4 wheels hang (I’d use jackstands and jacks) for this?

This came up in another thread recently and I think @Doubeleive or @Trey Hardy had some input.

Big Mama said:

This came up in another thread recently and I think @Doubeleive or @Trey Hardy had some input.

Click to expand...

Weren’t me I’ve not had much experience with the stock air suspension besides deleting it all together I’d personally felt like it was so much going on I’d rather have normal shocks that I ain’t gotta worry about 12 different things going bad on maybe @Doubeleive has some input

ReaperHWK said:

2015 Tahoe LTZ

I just replaced my suspension controller and repaired some wires. Some wires shorted and blew out the controller. Fixed wires and installed new controller all the errors went away and the computer can talk to the suspension controller(BCM and my scanner now). I can also do active tests and see that all the data is good between every shock and the controller. Looks like I’m back in business!


However all the shocks are totally flat; my scanner has a function to pressurize the system but it’s not clear (to me). I assume I do this procedure and then do the shock level initialization my scanner also has? Here is a screen shot of the scanner for the pressurization before it starts.

View attachment 434508

Do I just let all 4 wheels hang (I’d use jackstands and jacks) for this?

Click to expand...

you only have 2 air shocks (rear) they should not be flat unless there is a leak or the air line is removed.
they run on a loop of air not individually so they are either both inflated or both flat.
if you are attempting to do the ALC relearn then wheels on the ground, full tank of gas, vehicle unloaded, parked on a level surface
then just follow the directions it only takes like 1 minute to do.

Doubeleive said:

you only have 2 air shocks (rear) they should not be flat unless there is a leak or the air line is removed.
they run on a loop of air not individually so they are either both inflated or both flat.
if you are attempting to do the ALC relearn then wheels on the ground, full tank of gas, vehicle unloaded, parked on a level surface
then just follow the directions it only takes like 1 minute to do.

Click to expand...

Yeah I figured that out lol. I jacked up the rear and let the scanner pump up the shocks. The truck rose about 1” and the sensor for the height went to 1.6v compared to 0.3v when it’s deflated. So I know the SCM is getting feedback of where the height of the shocks are. So I am able to command the air shocks to inflate and they deflate after a few minutes of driving. The SCM won’t command them to pump up though without the scanner. I also inflated them, and used the command to deflate and that doesn’t work. The compressor also sounds like a bag of rocks when it is on. I’m thinking maybe the deflating part of the pump has a leak and doesn’t work because even the scanner can’t make it work…..

I’ve been driving the truck for a week to see if any codes are throw. But I’m leaning toward replacing the air pump now.

Trey Hardy said:

Weren’t me I’ve not had much experience with the stock air suspension besides deleting it all together I’d personally felt like it was so much going on I’d rather have normal shocks that I ain’t gotta worry about 12 different things going bad on maybe @Doubeleive has some input

Click to expand...

Very true lots of pieces in this system to fail. Good thing is I’m narrowing it down slowly though and getting closer to it finally working…. I already repaired damaged wiring and a fried SCM module and the truck throws no more codes and I can see all the shock data. I’m going to get the oem system to work because I think I’m almost there.

ReaperHWK said:

Yeah I figured that out lol. I jacked up the rear and let the scanner pump up the shocks. The truck rose about 1” and the sensor for the height went to 1.6v compared to 0.3v when it’s deflated. So I know the SCM is getting feedback of where the height of the shocks are. So I am able to command the air shocks to inflate and they deflate after a few minutes of driving. The SCM won’t command them to pump up though without the scanner. I also inflated them, and used the command to deflate and that doesn’t work. The compressor also sounds like a bag of rocks when it is on. I’m thinking maybe the deflating part of the pump has a leak and doesn’t work because even the scanner can’t make it work…..

I’ve been driving the truck for a week to see if any codes are throw. But I’m leaning toward replacing the air pump now.

Click to expand...

the pumps are sort of dumb devices they can be completely screwy and not cause a code. I had one once that would inflate to some wild numbers and would give erratic info sitting perfectly still anywhere from 0-100 psi, it would inflate to anywhere it wanted instead of 20-30psi with no load.

The compressors are noisy. Though I will say the oem was quieter than the dorman I replaced it with.

Check Rockauto for discount pricing plus they have a code for extra 5% off.

Doubeleive said:

the pumps are sort of dumb devices they can be completely screwy and not cause a code. I had one once that would inflate to some wild numbers and would give erratic info sitting perfectly still anywhere from 0-100 psi, it would inflate to anywhere it wanted instead of 20-30psi with no load.

Click to expand...

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?