Chevrolet 1994 Astro Passenger Owner's Manual page 116

If the warning light comes on, there could be a brake problem. Have your
brake system inspected right away.
This light should come on as you start the vehicle. If it doesn't come on
then, have it fixed so it will be ready to warn you if there's a problem.
If the light comes on while you are driving, pull off the road and stop
carefully. You may notice that the pedal is harder to push. Or, the pedal may
go closer to the floor. It may take longer to stop. If the light is still on, have
the vehicle towed for service. (See "Towing Your Vehicle" in the Index.)
The brake system warning light will also come on when
YOU
set your
parking brake, and it will stay on if your parking brake doesn't release fully.
If it stays on after your parking brake is fully released, it means
YOU
have a
brake problem.
Anti-Lock Brake System Warning Light
Standard Cluster
Digital Cluster
I
With anti-lock, this light will go on when you start your engine and may
stay on for several seconds. That's normal. If the light doesn't come on,
have it fixed so it will be ready to warn you if there is a problem.
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