GMC 2002 Sierra - Manual (Page 108)

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Automatic Transmission Operation If your vehicle is equipped with an automatic
transmission, it features an electronic shift position
indicator within the instrument panel cluster. This
display must be powered anytime the shift lever is
capable of being moved out of PARK (P). This means
that if your key is in OFF, rather than LOCK, there will
be a small current drain on your battery which could
discharge your battery over a period of time. If you have
to leave your key in the ignition in OFF for an extended
period, it is recommended that you remove the IGN 0
fuse from the instrument panel fuse block. See “Fuses
and Circuit Breakers” in the Index.
There are several different positions for your shift lever.