2006 Toyota Tundra Owners Manual - Page 180
2006 Toyota Tundra Manual
Page 180 highlights
'06 TUNDRA_U (L/O 0508) If the indicator or buzzer comes on... Do this. Remove key. (p) Key reminder buzzer (q) Four −wheel drive system warning buzzer Shift the transfer mode correctly. 180 2006 TUNDRA from Oct. '06 Prod. (OM34458U)