What is a sign of a problem with air suspension?

A deflated air suspension is a clear indicator of a problem within the air suspension system of a vehicle. Air suspension systems use air-filled bags or bladders to provide a smooth ride and maintain vehicle height. When these bags lose air or become punctured, the suspension cannot function properly, leading to a lower ride height, which may affect handling and comfort.

In contrast to the correct answer, frequent tire rotation needs could be related to various factors including driving habits or tire misalignment, but they don't specifically highlight a suspension issue. Abnormal rattling noises might indicate loose parts or other issues but are not exclusive to air suspension problems as they could arise from multiple other sources. Similarly, inconsistent braking performance can stem from many issues like brake wear, hydraulic problems, or wheel alignment, and isn’t directly linked to the state of air suspension unless the vehicle is significantly low to the ground affecting brake function indirectly. Thus, observing a deflated air suspension directly points to a malfunction in that specific system.