Ok, first off don't remove the bulb that is the "hard way" of correcting the problem.
There is a "sensor" mounted to the inside of the dashboard.
It's up inside the glovebox opening next to the key-in/seatbelt/lamps-on
warning buzzer
1)Remove all items from the glovebox
2)Squeeze in the sides of the glovebox "box" and allow the empty open glovebox
to hang straight down.
3)Unscrew module from lip of glovebox opening
4)Disconnect module from wire connector.
DO NOT STOP HERE!!!
5)Disassemble case of this unit and REMOVE circuit board
(This unit is officially called "Infered mileage sensor" it's essentially an
engine-hours timer)
6)Reassemble case, reconnect wire connector and re-install unit.
7)put all your crap back into the glovebox.
There is a "Reset" method for the unit to "zero" the timer but if your experience
is anything like mine (with no less than SIX different IMS units) you can follow the instructions and push that reset until hell freezes and it won't reset.
If you simply disconnect the wire it'll constantly get tangled in the glovebox
every damned time you open it.
The empty shell of the unit makes a nice "keeper" for the cable and in any area where someone MIGHT visually inspect "emissions system components" it will APPEAR to be there....
But in truth the unit does NOTHING except turn on the stupid light.
FWIW the time the lamp comes on is not even relevant because after
the trucks were made and rhe units installed Ford doubled the service
interval for the components that unit was reminding you to replace,
and not long after that the service interval was changed (again) to
"replace it when it fails"...
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