[HummerMann]

It's either the air bag or the sensor. Pretty common problem on older air suspension Hummers, however 3000 is way out of line. It should be 200 to replace a sensor or 500 to replace the air bladder. My '06 has the original air suspension with no problems so far. If you look through previous threads you will find it is common for the replacement sensors to be installed incorrectly. There's lots of previous threads on this and an especially good one by HumTech if you use the search feature. IMHO I wouldn't describe 36,000 miles on any vehicle as almost brand new, particularly a 4 X 4 that has been offroaded.