Most models of the Lexus LS400 sedan are designed with an antitheft system. If any of the doors, the boot or the hood is forcibly unlocked, or the battery terminal is disconnected and reconnected with the vehicle locked, the alarm will activate. The alarm blows the horn intermittently and flashes the taillights, headlights and other exterior lights when it is activated. The system will also immobilise, or lock, the engine until it is reset.
Turn the ignition key to the "LOCK" position. Remove the key.
Close and lock all the doors, the boot and the hood. Wait about 30 seconds until the security indicator flashes.
Insert the key into the driver or passenger front door. Unlock the door. The indicators flash twice to indicate that the system has reset.