I recently purchased a 2006 Lexus IS 250 & the battery was low in the key fob.

I replaced it myself, and it worked fine. After driving back home, I came inside for 15 mins and back out and the key isn't being detected and I just tried to turn the car on and it won't start?

Please, all tips and info are helpful! Thank you very much!

 

You sure it your FOB? The display on the dash will say low key battery. I would take the battery out and put it back in. Or hold the fob close to the start button if it lights up or not to start.

 

that is very weird. I'd say make sure you buy a couple more spare batteries to keep in your glove box, make sure you know how to unlock and lock your doors using the key insert on your fob. and go see your dealership if the problem persists.

 

When the car won't start, will it start if you touch the key fob to the start button, and press it? If so, maybe you just had a bad battery in the fob...