Chevrolet 2004 Impala Owner's Manual page 156

Anti-Lock Brake System Warning
Light
3-34
If your vehicle is equipped
with anti-lock brakes, the
anti-lock brake system
warning light should come
on for a few seconds
when you turn the ignition
key to ON.
If the anti-lock brake system warning light stays on
longer than normal after you've started your engine, turn
the ignition off. Or, if the light comes on and stays on
when you're driving, stop as soon as possible and turn
the ignition off. Then start the engine again to reset
the system. If the light still stays on, or comes on again
while you're driving, the anti-lock brake system needs
service and you don't have anti-lock brakes.
The anti-lock brake system warning light should come
on briefly when you turn the ignition key to ON. This
is normal. If the light doesn't come on then, have it fixed
so it will be ready to warn you if there is a problem.