Bad fuse or bad brake light switch.
Often these are accessed thru the trunk; have you tried that?
Check the brake light switch on the brake pedal
If you mean the brake lights are stuck on, then check the stoplight switch located on the top of the brake pedal.
The white parts of the tail lights are the reverse lights.
The cruise system shares fuses with the engine and brake lights. If the car runs and the brake lights work, it is not a fuse.
Inside the trunk there is a turnable thumb screws where the brake lights are. Twist screws off and the brake light pops out.
If the brake lights do not work on Chevy Venture van 2000, try to disconnect the brake switch. Then short the two contacts of the connector to check if the brake lights are now working.
check the fuse, brake lights have their own, & check the brake switch at the top of the brake pedal
bulbs blown on high side or wiring shorted
If all the bulbs are good then it may be a blown fuse or a defective or mis-adjusted brake light switch.
check your brake fluid level under the hood. This may be true if the brake light is in the dash . If the light your talking about is the actual brake lights on the rear of the car you probablly have a short in the steering column
Check the brake switch at the pedal.