Ok. So lately, my car doesn't want to turn on with my spare key. When ever I try to turn it on the alarm rings and keeps ringing until I disconnect the battery. I bought this car with only the spare key. So here's my issue. I need a new car battery, but the damn thing doesn't want to start. What do I do. Is there a way to reprogram the spare key to work??

 

I'm pretty sure you're gonna need to get your car to a Lexus dealer to have them sync a real key for it. I've had to do that on so many cars. Its $60-120 normally depending on how dumb they are. They often times claim they have to charge you diagnostic work then a new key then time to program it even if you just tell them to get you a new key.

 

I've got my two master keys but their so haggard I've had to tape them up. I disabled the keyless entry so only way my alarm is armed is by setting it myself. As to your problem I would research programming a separate key fob, one like for a 4runner, to open the doors.

 

On the older cars you have to start the car with the coded key to turn it off. Its not the keyless entry function its actually an immobilizer attached to the ecu and routed to the alarm setup.