Howdy folks,

So I tried searching up and down but it seems most people have the opposite problem (pressure decreasing). I'd like to explain my problem, what I think will fix it, and see what you all think.

Faults:
Yellow Suspension Fault Lamp
Always throwing C1A11-64 "Pressure increase when system inactive"
Once threw C1A13-64 "Pressure does not decrease when venting gallery"

Live Observation/Datalog
While datalogging on GAP tool, I was able to see what is actually happening to throw this code. Gallery pressure sits around 25-30psi...while idle, not moving, level ground, and compressor off, gallery pressure suddenly jumped rapidly to 130psi. System corrected this by opening exhaust valve briefly. Normal operation and pressure thereafter (except fault lamp still active and no height change or special programs)

Theory:
I suspect failing center valve unit (near compressor). The rise in gallery pressure could only be coming from the reservoir as compressor is off and no logged change of corner valves. I imagine the solenoid is weak perhaps and fluttering open ever so slightly on occasion causing this problem. The other code, relating to exhaust, would come from this same valve body so reinforces my belief that is root cause.

Notes:
Airbags a few years old, rear valve 6months old, AMK upgrade compressor/dryer/software upgrade 6 months ago, front valve supposedly only a few years old, center valve OEM (2005).

What do you all think?

Many thanks!

Here is the datalog with notations:

 

Your theory is sound, I would suspect the reservoir is leaking into the gallery also. You could try to disconnect the reservoir and cap the line. You may get a code complaining that is suspects the gallery is not filling or something, but with no stored air to escape back into the system you would know if its the issue.