FICM cause poor mpg's

[mrbucket1210]

ive noticed my ficm volts slowly dropping. ive also noticed my truck getting 12mpg's in the city. do ficms have anything to do with mpg's?

[HAM_RADIO_MAN]

I would think in some world it could, lets think about this. If the FICM output wave form was not letting the injection event happen properly you could see lower MPG. If the output wave form was low on voltage and that caused the injector to open slowly or late you would losing power by not getting fuel in the right time, thus retarding injection timing. The injector closing slowly would be wasting fuel by injecting it late in the combustion event possibly leading to unburned fuel, this is why trucks with bad FICM’s sometimes smoke. So YES, anytime you loose power or have unburned fuel you loose MPG.