GMC 1994 Yukon Owner's Manual page 134

You can only drive for a short time with the reading in either warning zone.
If you must drive, turn off all unnecessary accessories, and have the vehicle
serviced as soon as possible.
Center High Mount Stop Lamp (CHMSL)
Your vehicle has a
Center High Mount
Stoplamp (CHMSL)
located above the
tailgate glass or above
the rear load doors.
If items are loaded on the roof of the vehicle, as in a luggage carrier, care
should be taken not to block or damage the CHMSL unit.
Convenience Net
If you have a convenience net, it is stored i n
a pouch attached to the spare
tire.
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