My truck was low on antifreeze so I filled the.

Brake fluid is probably low too. If there's a level sensor in the side of the master cylinder, unplug it to see if the light stays out. If it does, add a little fresh, clean brake fluid, absolutely NOT a single hint of petroleum product such as engine oil or power steering fluid. Don't fill the reservoir to the top. The fluid is either low because the front pads need to be replaced or there's a leak. Both concerns should be addressed right away.

The parking brake pedal could be not fully released too. When the brake light turns on, try pulling the pedal up with your foot.

The third cause is a leak in one of the two hydraulic systems. Unequal pressure will trip the warning light. GMs and Chryslers have spring-loaded switches so the light normally will go off when you release the brake pedal.