Use a dime to open the key fob battery door on the key fob. New batteries are typically available at Radio Shack. Salesperson at same usually know how to open it.
Open it up and check and see.
To change the battery in a 2007 Lexus IS 250 key fob, first, use a small flathead screwdriver to gently pry open the fob along the seam. Once open, remove the old battery, noting the orientation, and replace it with a new CR1632 battery, ensuring the positive side faces up. Reassemble the fob by snapping it back together until it clicks. Test the key fob to ensure it operates correctly.
Bad battery or alternator, or simply ran out of gas
The 2008 Lexus IS-250 has a V6 engine.
The 2014 Lexus IS-250 has 24 valves.
The 2010 Lexus IS-250 has a V6 engine.
The 2013 Lexus IS-250 has 24 valves.
The 2009 Lexus IS-250 has a V6 engine.
The 2006 Lexus IS-250 has a V6 engine.
The 2013 Lexus IS-250 has a V6 engine.
The 2012 Lexus IS-250 has a V6 engine.
The 2012 Lexus IS-250 has 24 valves.