Locate the small silver switch on the bottom of your Lexus ES350 keyless entry fob. Slide the switch all the way to the right and remove the mechanical key from the electronic fob.
Examine the keyless entry fob to locate the small groove that was revealed by removing the mechanical key. Insert the tip of the mechanical key into the groove and work it back and forth until the halves of the electronic fob separate.
Use the tip of the mechanical key to pry the old battery out of the battery compartment; insert a new CR2032 battery, making sure to observe the correct polarity. Note that the battery compartment is mounted to the back of the circuit board in the electronic fob.
Align the two halves of the electronic keyless entry fob. Use your fingers to apply gentle to moderate pressure to both halves of the fob until they snap together.
Reinsert the mechanical key into the Lexus ES350 electronic fob. Push in the mechanical key until you hear it click into place.
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If you have recently purchased a spare remote or just replaced the battery in your backup Lexus key fob, you probably need to reprogram the remote to work with your car. You can take the new or malfunctioning key to a Lexus dealer and have the key reset in no time for a charge ranging from $50 to $75. With just a little time and patience, however, you can do the reprogramming yourself and save some money.
Close and lock all the doors of your Lexus, then unlock and open only the driver's door.
Leave the driver's door open and insert the key into the ignition, but do not turn it. Remove the key from the ignition.
With the driver's door open, lock and unlock the doors five times with the electric lock switch in the car. Take care to complete five lock/unlock cycles, ending on unlock.
Close and open the driver's door.
Repeat the lock/unlock cycle performed in Step 3.
Insert the key into the ignition, and turn the car on. Turn the car off, and remove the key.
If the locks did not cycle, start over from the beginning. If the locks do cycle on their own, meaning they lock and unlock at each door, press the "Lock" and "Unlock" buttons on the remote simultaneously for no more than two seconds.
Press and hold the "Lock" button for one second. The locks should cycle once, which means your Lexus has accepted the new remote. If the locks cycle twice, the reprogram was not successful; start over from the beginning.
Close and open the driver's door to complete the reprogram on the remote.
If your first attempt fails, try performing steps 7 and 8 from outside of the car, which may help improve the signal strength between the remote and the car.
