F 150 Heritage 4WD Pickup V8-5.4L SOHC VIN Z Bi-fuel (2004)
Alternative Fuel Selector Indicator: Description and Operation
Bi-Fuel CNG Models
ALT/GAS INDICATOR
The ALT/GAS switch indicator is integral to the ALT/GAS switch. The indicator is controlled by the AFCM and is illuminated when operating in
CNG mode. If an emission-critical diagnostic trouble code (DTC) is recorded, the indicator will flash with a steady ON, then OFF pulse.