Suspension Codes C0585.04 / C0585.01


TYF Newbie
Aug 4, 2020
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The Lonestar State
Upon purchasing this used ‘08 LTZ, when getting a shop to install a new evap solenoid & charcoal canister, I mentioned to them about a suspension warning message and they took a look at it -

Upon inspection (non dealership) they noticed the compressor pump had been unplugged, and ask if I wanted them to plug it back in, I said of course because I wanted to know the condition of the rear z55 system I didn’t even know I had. (my last ‘07 was not z55.)

Needless to say, the pump functions briefly when the ignition is set to on within 10–15 seconds, and at startup it activates same duration or sometimes even when the engine down. So the pump up until this point has been trying to work consistently. Shop said rears were blown out (took a look myself, was pretty obvious) - I replaced with OEM comparable rears from amazon to save on some money on parts - shop installed and let me know original wiring to the pump was tucked away as if the previous owner might have tried to bypass… (not sure why they would run oem shocks with a bypass? I digress)

When getting some work done from a buddy a few days later, I had him use his tech tool and see what the suspension codes were that come back even when I clear them with my cheaper scanner - C0585.4 and c0585.1

Tonight I finally took a look at the pump and new shocks, and the airline to left driver rear appeared disconnected
, most likey while driving ( there’s very little slack in it) so I attempted to put it and the little pin back onto the shock after hearing the pump was attempting to force air. No change in ride height.
As soon as I start the truck I can hear air out of this connection line - I don’t know now if its “working” correctly or not, but I did also notice there was a 3 pin connector harness on top of the compressor box that wasn’t connected.
Tomorrow I will try and provide some images for reference.

I have a few questions at this point:

first, I’ve researched these codes with little definitive or examples of my issue -

is this a pump malfunction? it appears it has been replaced and isn’t the original due to lack of wear. It seems like it is in working order as it doesn’t run all the time, only at startup or shut down -

is this a hose/line since theres little to no slack to keep the rear driver line attached at the end? I’ve seen dorman replacement line kits, is that an easy thing to do?
Is this the shock? The pair is brand new and the codes are only for the left side, and Ive had this suspension warning before I even replaced them…

or is this purely electrical, like a problem with the ESCM, and if so, where is this located and is this a pain to jack with?

Lastly, what are these codes and for cost (i’m on a very tight budget) is it better just to bypass this whole system entirely? If anyone has replaced any of the harnesses or connections, do you have a writeup or photos/tutorial on how to repair it?

- Any help is much appreciated, thanks.

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