FORD 2013 F-550 v.2 - Manual (Page 227)

System indicator lights and messages
WARNING: If a failure has been detected within the Traction
Control System, the stability control light will illuminate steadily.
Verify that the Traction Control System was not manually disabled
using the stability control button. If the stability control light still
illuminates steadily, have the system serviced by an authorized dealer
immediately. Operating your vehicle with Traction Control disabled
could lead to an increased risk of loss of vehicle control, vehicle
rollover, personal injury and death.
The stability control light temporarily illuminates on engine
start-up and flashes when a driving condition activates the
stability system.
The stability control off light temporarily illuminates on engine
start-up and stays on when the traction control system is
turned off or if a problem occurs in the stability system.
226 Traction Control
2013 F-250/350/450/550 (f23)
Owners Guide gf, 2nd Printing, December 2012
USA (fus)