jsculley

For anyone with poor fuel mileage on a 2004.5 with cummins 600. My truck has 21K miles on it and has averaged around 13 mpg from day one; that's what I see on the computer and roughly what I calculate when I fill up. It has a lift and 35" tires so I expected less mileage than the '97 12 valve I traded in. Yesterday I had my dealer take care of several small issues. One thing they did was reflashed my ECM per TSB 1803704 to address the fuel mileage issue. They also recalibrated my spedo which was off due to tire size. The overhead computer now reads aroud 17-19 mpg with in town driving! I expect to calculate something close to that after running a full tank of fuel. If you have an '04.5 and haven't had the reflash done, I recommend it highly!!

Mixer Man

I agree ....... the white smoke flash really helped my mileage & toned her down a bit on part throttle response . I am convinced the mileage discrepancies are mostly due to garbage fuel quality . My truck gets right at 20 mpg IF I crawl down the highway under 65 which is becoming the norm now that fuel is running 2.50 /gal here !! Drove Cummins powered concrete trucks for 10 yrs & all fueled from the same tank at the plant and mileage was nearly identical all on all 60 trucks . Very few injector probs & driver has alot to do with mileage also .

fwd talon

when i keep my foot out of mine im getting around 22- 23 mpg. and yes the reflash is worth it.

triplenickle

I hear so much about this "reflash" that everyone talks of. I know next to nothing about electronics and computers, i was wondering, what is it that is done as part of a reflash? Is it something that is under warranty, and how would i tell if my truck needed it? Are most dealers pretty good about doing a reflash, since there isnt anything visibly "broke" on the truck?

jsculley

My dealer did it under warranty no questions asked. I still need to run a full tank through and calculate the mileage, but I expect my mileage improved aprox. 4-5 mpg.. Good luck..

300 SDL

Reflashed on two (2) occasions. No fuel mileage change.

RamWheelsBy4

The TSB flash did not change my mpg any. The TSB says potential 1mpg increase and I would not expect more. If you just had ECM "Pinion Factor" programmed for the 35" tires, what correct factor have you been using to hand calculate mpg. The overhead should not have been anywhere near correct.