bmw 2002 x5 reboot to start air pump

[pukespuey]

hi

newbie here. just bought my first bmw. i love it! i have a 2002 e53 4.4i v8. its a truly awesome machine, just glides along. i can't wait to upgrade the mufflers to release the growl sound!
however, it seems i have bought one with a few issues:
with the rear air suspension- im pretty sure there is a slow leak on the rear left side because it is sometimes dropped lower. but once i open the car door it pumps back up.

the other day it was lower but when i opened the door the pump didnt work. i read that if you disconnect the battery, wait ten mins and then hold the +ve -ve leads together 20 seconds it resets the computer with a"click" sound. so i did this but didnt hear any click. but, it did pump up once i reconnected the battery!

today however, both rear sides have dropped flat and the air pump wont engage. i tried disconnecting the battery and touching the terminals together but still no pump. its almost undriveable!

can anyone clarify what needs doing to reset it?

regards
jason