My overhead computer readout display for average mpg is way off. It reads approximately 10 mpg more than it should. All the other readouts seem to be correct (except for the distance-to-empty, which I'm guessing is based on the mpg results). Is there a way to calibrate, or re-calibrate the computer/display to make it more accurate? Thanks.

 

The only TSB for SD trucks or 6.0L motors is the following... but it is not an exact match for your problem (thought I would share anyway).

Overhead Trip Computer Distance to Empty Reading Incorrect:Trucks built after 11-18-02 may have an incorrect DTE reading displayed on the OTC. The OTC will need to be reprogrammed using As-Built data matching the specific tank sizes listed in TSB #04-15-10.

The other option is to disconnect both batteries, wait a few minutes and reconnect. This may or may not reset all computer functions, but it is worth a try? Your truck will run rough as it relearns computer, driving, and transmission settings... but it is a "no cost, safe" approach to seeing if it works? It may allow your truck (may take 2 tanks of fuel) to learn total miles left of fuel and average mpg???

The only other option is to see if a re-flash for your computer is available as this resets and brings it up to all current computer, fuel injection and transmission settings (some have had good luck with this and others not so good luck).

These are your only options that I can think of... so good luck.

 

You are resetting it at every fill-up aren't you? If not, then it may be the cumulative total of the typical error (usually 0.3 to 0.5 MPG ... mine's typically off by 0.4 MPG) from who knows how many fill-ups. I like the idea of disconnecting the batteries to reset it.

 

Thanks for the help, guys. I forgot to mention I have a superchips programmer installed. (It came w/the truck when I bought it.) Could this somehow be causing the mpg readout misrepresentation? In addition, I'm assuming if I disconnect the batteries it would cause the programmer to go back to the stock setting.

 

Yes. People have reported that happens. I was checking my mpg and it was pretty accurate. DP-Tuner programmed PCM and the first time it was off 0.5 mpg. Have to check more.

No. The programer has made it's program the "stock" setting.

 

I have an '05 Limited 6.0 -- the mpg thing is seemingly accurate "instantaneously" but the cumulative number is optimistic to say the least. On a 44 gallon tank, I'd expect to use 40 gallons, which at 15mpg, should see 600 miles, right? But the lie-o-meter (as it's called around here) almost invariably shows an average of 15 but the tank is empty between 500 and 600 miles and needs about 40 gallons (or about $135.00) to fill up to the first click meaning the real average is below 15. On the highway, it suggests 18mpg but the trip meter rarely sees 700 miles, so still less than expected.

I find the "distance to empty" is pretty smart if not all that accurate. If I half fill the tank (or at least I don't go over $100 at once just to preserve my temper) I notice it goes optimistic (800+ DTE) then it adjusts to the actual fuel level (somehow?)

The DTE is pretty consistent -- once it say "0" I have about 50 miles comfortably in the tank and the diesel has a sort of "limp home" behaviour if I run the tank to the last drop (which has happened twice so far) it will start to lose rpm (but run smoothly at idle) and have just enough oomph to crawl along at 10mph ... which has saved me a couple of mile walk on both occasions.

 

I have gotten within 2 tenths of the actual mileage since I have 3 decimal places to go with for the fuel and 1 for the mileage and only 1 for the meter.

 

I guess my lie-o-meter must be on steroids. According to it I'm averaging somewhere between 26 and 30+ mpg on a consistent basis, whether I reset it each fill-up or not. That is a mix of city and highway driving. My actual mpg is usually between 16-18.

 

Maybe it is set for imperial gallons.

Are you in canada?

It can be changed, I read it in my owners manual.

 

Thanks for your idea, Huck. I never thought of that possibility. The X has spent its whole life in the states, but I'll check out the possibility.

 

I looked in my owner's manual and all I could find is how to change from english to metric units (gallons to liters).

 

my solution to the lie-o-meter...



Though it is nice knowing MPG on the go, its not really needed. just think about keeping your foot out of it and that tends to help me more than looking at a number that could be right, or could be way off. We need to get some computer guys like Jody on this and see if they can't do something about it. Other than that, I don't think its going to be worth your time. I could be wrong though!