Ford F-650 2015 Owner's Manual page 158

System Indicator Light
Note: If the traction control light does not flash during a traction control
event or stays illuminated, the system is not functioning properly. Take
your vehicle to an authorized dealer for service.
During traction control operation, the traction control light
flashes rapidly and the engine does not rev-up when you press
further on the accelerator. This is normal and is no reason for
concern.
In Off Road or Mud/Snow mode, the traction control light illuminates and
flashes slowly. If a traction event occurs, in either mode, the light flashes
rapidly.
2015 F-650/750 (f67)
Owners Guide gf, 2nd Printing, April 2014
USA (fus)
Traction Control 157