Final answer:
When the low-pressure warning light comes on, the crucial step is to stop and park safely to prevent accidents and check the vehicle for issues.
Step-by-step explanation:
The most important thing to do when a low-pressure warning light comes on is to stop and safely park as soon as possible. This warning light usually indicates a significant loss of air pressure in one of your vehicle's tires, which can lead to tire failure and potentially cause an accident if not addressed immediately. By stopping and checking your vehicle, you can ensure your safety and prevent further vehicle damage.