Lexus GS300 1998 Owner's Manual page 26

KEYS AND DOORS
D When starting the engine, do not use the key with
other transponder keys around (including keys of
other vehicles) and do not press other key plates
against the key grip. Otherwise the engine may not
start, or may stop soon after it starts. If this happens,
remove the key once and then insert it again after
taking off other transponder keys (including keys of
other vehicles) from the ring or while gripping or
covering them with your hand to start the engine.
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