The parking brake warning light should come on whenever the parking brake is applied or not fully released. On some vehicles, this light can be confused with red brake hydraulic system warning light since it's also red in color.
The Bulb Check: Parking Brake Warning Light
When the ignition key is rotated through the phases of Off, Run, and Start, a brake systems bulb check is activated. Both the brake hydraulic systems red light and the parking brake light will illuminate. If there are no problems detected in the brake hydraulic system, the red light will go out after 1 to 2 seconds. If there is a problem detected, then the red light will stay on.
As long as there are no problems detected in the parking brake system, the parking brake light will stay on until the parking brake is completely released. On some vehicles, these lights look very similar, so make sure you know where each light is located in the instrument panel and what its purpose is.
It is always a good idea to check your vehicle owner's manual and familiarize yourself with your vehicle's warning lights. This way, there is no confusion as to which warning lights should be on and which should not.
What to Do: Parking Brake Warning Light
If the parking brake light does not go off after the parking brake lever has been released, jiggle the handle to make sure that the mechanical part of the parking brake system has been completely relaxed and that there is no tension on the cables or levers. If the light is still on, see if the vehicle moves without any drag. This can be done by moving the vehicle in a forward direction and then putting it in neutral. If the vehicle rolls very freely, then there may be a problem with the parking brake light switch and not with the parking brake mechanism itself. If you feel a pull, there is a problem with the parking brake mechanism.
In any event, if the parking brake light stays on when it should not, have the vehicle properly diagnosed and inspected at a qualified repair shop.