You may have the wrong remote. Many of the Lexus remotes look the same, but the electronics are different. here are some instructions on how to program the remote into the car. If that doesn't work, you may want to purchase a new remote head key for your car & try to program it. Check out the the following website if you need more help. http://www.sparecarekeys.com
1. Remove the key from the ignition switch. Open the driver’s door. Make sure that all other doors are closed.
2. Insert the key into the ignition switch, then remove it.
3. Press the LOCK and UNLOCK on the vehicles door lock control switch at one second intervals five times.
4. Close and re-open the drivers door
5. Press the LOCK and UNLOCK on the vehicles door lock control switch at one second intervals five times.
6. Insert the key into the ignition switch.
7. Switch the ignition ON and OFF once to program a key remote transmitter code, while retaining the original codes.
8. Remove the key from the ignition switch. System should now lock and unlock the vehicle once. System will then lock and unlock the vehicle one to four times slowly to indicate the number of key remote transmitters registered.
9. Press and release LOCK and UNLOCK buttons together.
10. Press any key remote transmitter button for a minimum of one second. System should now lock and unlock the vehicle once to confirm registration, twice will indicate registration has failed.
11. If required, repeat button procedure to program remaining key remote transmitters.
12. To exit programming mode, Close driver door, or insert the key into the ignition.
***NOTE: A maximum of 4 remote transmitters can be programmed.