Another 'selflevel susp inact' thread

[e39_touring]

We bought this '05 X5 3.0 with the 4-wheel air suspension that had a big leak in one of the front air springs (lowrider in the front). I replaced both front springs (with the Arnott spring-only solution) as well as both front axels with EMPI brand.

Got everything back together and used INPA software to activate the pump a few times to pressurize the system. No leaks - good. I reset all the trouble codes and test drove.

However, a day later, the dreaded 'selflevel sus inact' warning reappears. The car has not sagged at all while sitting; so, I don't think I have any leaks.

I pull the code using INPA and then reset. The code is 'filling of reservoir requested, but pressure doesn't increase'. I reset it just to see what happens, but it keeps coming back - sometimes after 10 minutes or sometimes after a few days of driving.

I then fired up DIS and went through the full diagnostic, which tests everything related to this code. Observer pressure in accumulator - OK, 11.6 bar, turn compressor on - OK, observe pressure in acccumulator - 12.9 bar, open dump valve - whoosh, observe pressure in accumulator - 9.6 bar.

As far as I can tell, this error should only be caused by: 1) compressor not turning on when called, 2) big leak in the accumulator, or 3) faulty accumulator pressure sensor. All three seem to check out.

This is driving me nuts!!! Any ideas what else could keep throwing this code. The only other thing I can think of is that I have an intermittent problem with either the compressor (sticky relay?) or pressure sensor (i.e. bad data, but not no data). I guess I have to 'catch it in the act', which we all know how tough that can be...