Up-Shift Light; Brake System Warning Light - GMC 2004 Sierra 1500 Pickup Owner's Manual

You can only drive for a short time with the reading in
either warning zone. If you must drive, turn off all
unnecessary accessories.
Readings in either warning zone indicate a possible
problem in the electrical system. Have the vehicle
serviced as soon as possible.

Up-Shift Light

The shift indicator light will show you when to shift to
the next highest gear, and will help you get the best fuel
economy.
This light is used on some
models with manual
transmissions.

Brake System Warning Light

With the ignition on, the brake system warning light will
flash when you set the parking brake. The light will
flash if the parking brake doesn't release fully. If you try
to drive with the parking brake engaged, a chime will
sound when the vehicle speed is greater than
3 mph (5 km/h).
Your vehicle's hydraulic brake system is divided into two
parts. If one part isn't working, the other part can still
work and stop you. For good braking, though, you need
both parts working well.
If the warning light comes on and a chime sounds there
could be a brake problem. Have your brake system
inspected right away.
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