Which sign might indicate low power steering fluid?

The option indicating a whining noise during a steering turn is significant when diagnosing low power steering fluid. This noise typically arises because insufficient fluid causes the power steering pump to work harder to move the steering mechanism, leading to cavitation or aeration of the fluid. When air is trapped in the fluid system due to low levels, the pump struggles to provide adequate pressure, resulting in the whining sound.

Observing this noise can serve as an early indicator that the fluid level needs inspection and possibly a refill. It's essential to address this issue promptly to prevent potential damage to the power steering system, as continuing to operate with low fluid can lead to pump failure and more expensive repairs.

The other signs mentioned, such as a loose steering wheel, vibrations, or the power steering light on the dashboard, may point to different issues within the steering system or other components but do not directly correlate with the immediate consequence of low fluid levels in the power steering system like the whining noise does.