What should be checked if the brake pedal feels soft or spongy?

When the brake pedal feels soft or spongy, the primary concern is often related to the air brake system. A soft or spongy pedal can indicate that there is air trapped in the brake lines or that there is a leak in the air system. This is crucial because air in the brake lines can compromise the hydraulic pressure needed for effective braking, leading to reduced braking performance and a potential safety hazard.

Inspecting the brake system for air leaks is essential to restore proper function. If there's a leak in the air system, it can lead to a drop in pressure, resulting in the brake pedal feeling spongy. Addressing this issue typically involves bleeding the brakes to remove any trapped air and correcting any leaks identified.

The other options relate to different systems or components of the vehicle that do not directly impact the brake pedal's feel. Checking tire pressure, inspecting the steering connection, and examining the fuel system, while important for overall vehicle maintenance, would not resolve a situation where the brake pedal feels soft or spongy, making the inspection for air leaks or air in the brake lines the critical step.