F 250 4WD Super Duty V10-6.8L VIN Z CNG (2003)
Speedometer Head: Description and Operation
The instrument cluster is hardwired to the four wheel anti-lock brake system (4WABS) module. The instrument cluster micro-processor monitors the
vehicle speed sensor (VSS) data from the 4WABS module and commands the speedometer with a corresponding movement of the pointer. The
vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed
signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input.