Just the one that losing air. I have not replaced mine and it's getting close to 300,000. You want to pull the spare tire out and check all the air fittings to make sure they are tight. You can all so spray soapy water on the air bag that is leaking and see if its the bag that is leaking or not. If it has a leak you will get soap bubbles where the leak is.

The one time I was have issues with my air spring, it turned out to be the sensor. There on each side. You could switch them and see if the problem persist.

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2010 X5M /// R63 AMG...Wifey's 540HP Family Hualer

2001 X5 3.0i Sport 335,448 miles & counting...
SMG M3 Steering wheel
E46 Stainless Racing Headers
4.6is Exhaust
Turner Pulleys
Afe Intake
Brembo drilled rotors
PowerFlex Bushings
Hualingan
30mm H&R Spacers rear
20mm H&R Spacers front
Bavarian Autosport High-Performance Coils
Active Autowerke's Performance Software