2006 tundra flashing red light on dash with key

I have a 2006 tundra and since yesterday have light on dash when I lock truck . It’s a red light with a key. When truck is unlocked the light goes off . When it’s locked light is blinking or sometime solid . Doesn’t effect truck starting . Tried new battery in key fob and tried disconnecting battery . I never see that light on truck since I bout it 9 months ago . Any thought

 

Does "crew cab" mean the same as what Toyota calls Double Cab(DC), if so, is this "red ight on dash" on right side of dash next to fuel gauge ?
If so, I believe you're speaking of your "Theft deterrent system" indicator, shown below from your 2006 Owners Manual pg 44.

1st Gen Tundra Brochures & Owner's Manual

 

This is the nicest way I've ever seen someone say, "RTFM!"