Ford 2005 05+ Mustang Owner's Manual page 152

Driving
3. Turn the key to 3 (ON) without
turning the key to 4 (START).
Make sure the corresponding lights illuminate or illuminate briefly. If a
light fails to illuminate, have the vehicle serviced.
• If the driver's safety belt is fastened, the
light may not illuminate.
151
2005 05+ Mustang (197)
Owners Guide (post-2002-fmt)
USA (fus)