overhead

I have the overhead buttons with the fuel economy and miles per gallon and such.....I tried searching this but found no luck. I put gas in my blazer and I never fill up my tank all the way. It is at about 3/4, but do you have to fill your tank up all the way for the overhead functions to work accurately (miles per gallon, how many miles before you run out, etc...) or is there a sensor that just knows how much gas you put in the tank. are these functions accurate at all?????? any help will be greatly appreciated

The system is calibrated to roughly calculate this information. I wouldn't rely on it 100%, but its a good indication of what you should get out of the amount of fuel you have in there, given the driving parameters you are doing etc, etc.

I don't have these buttons but I have the place for them. Anyone know if I can go to the junkyard and pull one out and hook it up easily or is it a major pain?

93gmc, you could get one to work, but its not just plug and play. You need to do some work to get it to work properly.