Suddenly developed a strange issue with my 2004 4.4 L322.
Driving the a few days ago and air susp fault displayed on dash.
Next day after a short drive the rear droopped fully followed by the front.
Fault code comes up as
18 - Supply, high pressure drain valve - short circuit to positive
75 - unknown fault code.

Diag tool I was using only lists air susp features under E53 section. So codes are BMW.

It is now fully deflated.
I can use tool to raise, compressor starts but never lifts.
Accumulator pressure is around 1 bar. I can deflate and set to inflate. That all seems to work correctly.

Spent a while more on this.
I have changed the valve block.
I have also swapped for an X5 compressor (used). Seems to have good pressure.
However, still the same symptoms.

Accumulator doesn’t seem to ever get above around 1.7 bar.

Anyone experienced the accumulator sensor failing?

See here for some ideas....

https://www.fullfatrr.com/forum/post542379.html#542379

You probably have a leak (in an airbag) somewhere, or a dodgy height sensor

Get codes read with proper diagnostics .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Would I be right in assuming the valve directs air to fill the accumulator. Therefore if an airbag had a leak it wouldn’t show until the vehicle tried to raise?