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New electronic throttle control assembly?

I recently had the electronic throttle control assembly replaced and my mileage dropped from 15.5 mpg to 12.5 mpg city. the hywy mileage stayed at 22.5mpg. Dealer and Independent say no adjustments. Why the mpg drop?

Since you don’t list the year, make or model of your vehicle it will be impossible to give you a definitive answer. The best guess however is that your vehicle computer (ECM) is in a “learning” mode right now since the electronic throttle control assembly was recently replaced. It may reach or exceed your 15.5 mpg estimation but only time will tell.

sorry, should have filled in the blanks. 04 Buick Rendevous Ultra 3.6 engine. ECM replaced 2 months ago and have driven 2K miles since.

just learned that there is a slight variation in the ohm value when the gas pedal is released. The no pressure on the gas pedal value varies between 1ohm to 3 ohms. Does that mean anything or is that within normal tolerance.

In addition to the year, make, model and mileage of your vehicle, it might also help us to know why the throttle control assembly was replaced. Could it be that the old one was broken and the new one correct? And the mode of failure caused a mileage variation?

Perhaps it defect didn’t allow you to “floor the pedal” and the new one does? Seriously, if the old one was unable to provide a signal to the ECU that allowed Wide Open Throttle (WOT) throttle and the new one does, your mileage will drop around town…and stay the same on the highway. Unless you, like me, like to pass on the highway.

old one was replaced due to a break in the wiring that shorted out the circuitry. the short circuit was fixed and the ecm (including the throat plate as dictated by GM) was replaced. I’m about as far away as you can be from being a mechanic but my gut says its something that is in the low ohm settings of the module.