If your vehicle is showing low brake fluid warning message on the instrument cluster, here are the most likely causes and the parts you'll need to fix each one.
As brake pads wear down over time, the caliper pistons extend further out to compensate. This draws brake fluid from the reservoir into the calipers, naturally lowering the fluid level and triggering the warning.
Corroded metal brake lines or cracked rubber brake hoses can develop leaks, causing a rapid and dangerous loss of brake fluid and hydraulic pressure.
Worn piston seals inside the brake calipers can fail, allowing brake fluid to leak out around the wheels and depleting the reservoir.
If the brakes were recently serviced, the technician may have failed to properly bleed air from the system or forgot to top off the reservoir after compressing the calipers.
The master cylinder can leak fluid externally or internally into the brake booster. This causes fluid loss and a spongy pedal, often without leaving obvious puddles under the wheels.
The fluid level sensor or its internal float mechanism inside the reservoir can fail or get stuck, triggering a false low fluid warning even when the reservoir is completely full.