A rotted brake line, a leaky front caliper, a leaky rear wheel cylinder, a leaky master cylinder,
Bad brake booster.
Check you brake fluid and lines. It may be as simple as bleeding your brakes.
When a brake line is leaking on the Chevy Venture the brake line should be replaced as soon as possible. A leak, however small, can cause hydraulic fluid to escape the brake line which will cause a loss in brake pressure. The brakes should be bled of air after the new line is put in to remove gaps in brake pedal pressure.
This is a sign that you need to have the brakes inspected, soon. Worn brakes causes the brake fluid reservoir level to drop causing the brake and abs lights to come on.
If it is a front brake problem it could be a frozen (stuck) caliper, collapsed brake hose or a pinched brake line. If it is in the rear it could be a frozen e-brake cable, pinched brake line or a frozen wheel cylinder.
it might not have enough brake fluid or your ABS is going bad. i would take it to a shop cause that can be serious.
The brake pedal has nothing to do with it. If air is in the system then bleed the brakes.
a wild panda tampering with your brakes
Sticking caliber. Flush the brake system and install fresh brake fluid, then bleed the brakes. If that does not help, replace both calibers and brake pads on the axle where the brakes are grabbing.
un equal adjustment of brakes will cause one brake to apply earlier and harder than other brake
warped brake discs can cause your brakes to grab in reverse. Hope this helps.
This is probably due to worn brake rotors on the brakes, if there is no vibration when driving then this will be the cause.