Lexus RX400h2006 Owner's Manual page 54

Flat key
As a transponder chip is built in its key case, you can start
the hybrid system with this key.
The flat key works in every lock.
A transponder chip for the engine immobilizer system has been
placed in the key case of the flat key. This chip is needed to
enable the system to function correctly, so be careful not to lose
this key. If you make your own duplicate key, you will not be
able to cancel the system or start the hybrid system.
Insert your flat key plate in its key case as shown. We
recommend that you always carry this with you for emergency
use. Do not leave it in your vehicle.
Starting the hybrid system using a flat key
1. Remove the key plate from the key case.
2. Insert the key plate into the ignition switch. The indicator
light keeps flashing.
3. Bring the key case closer to the ignition switch within 10
seconds as indicated by the arrow head. The indicator light
goes out. This means the engine immobilizer system is
automatically canceled. (For details, see "Engine immobilizer
system" on page 30.) You can put the key case away then. You
cannot cancel the engine immobilizer system if 10 seconds
have past after you inserted the key plate. You need to remove
the key plate from the ignition switch and try it again from the
step 2.
KEYS AND DOORS
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