Modifying tire diameter, is this correct?

[TheSEARCH]

Okay did it yesterday . Here is what I found out

UNDER Module tab on left You back up BdyCm first. Then run it. Then after running a bunch of choices in right pane. Search for circumference. Since my speedo said 60 mph but really was going 58 mph I adjusted the factory setting from 2221 to 2162. Then write that.

After that go to WRENCH tab on left and you need to run TWO things. First PCM Module, Then run IPC Module .

Then go to tab DTC on left see if any codes were set. In my case none were set. So I hit tab at bottom to disconnect forscan. Then unplug and shut off computer. DONE

NOW I take it for a ride and it seemed WORSE. Like 3 mph off. I am like WTF. I stop at store come back restart Mav drive home and see hey it looks correct . Now but only going 30 mph. I go to highway get up to 60 mph on speedo set cruise look at GPS and its dead on now. So it appears you have to drive once then shut of drive again to have settings take place.

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[Glen Baker LLC]

Why don't you just go into engineering mode on the dash and change the AFE setting to match your actual tires? No Forscan or anything else needed.

"Master Blaster"
I've never heard of the engineering mode. How do you display it?
Besides tire size, what other perimeters can be changed on it?

 

[Chops]

AFE just applies a correction % to the value that is calculated from the values that are read - doesn't change the base values.
Screens on each side of the setting screen show you the values used.

950 / 1000 - 95%. Just a correction %.

If you really want your DTE or displayed mpg to be right on - that's your solution.
But it won't correct your inflated driven miles reading, or speedometer.

Ahh, that makes sense. A correction factor on mpg is useful. A “correction factor” on the speedometer or odometer probably illegal.

 

[HeyBales]

Okay did it yesterday . Here is what I found out

UNDER Module tab on left You back up BdyCm first. Then run it. Then after running a bunch of choices in right pane. Search for circumstance. Since my speedo said 60 mph but really was going 58 mph I adjusted the factory setting from 2221 to 2162. Then write that.

After that go to WRENCH tab on left and you need to run TWO things. First PCM Module, Then run IPC Module .

Then go to tab DTC on left see if any codes were set. In my case none were set. So I hit tab at bottom to disconnect forscan. Then unplug and shut off computer. DONE

NOW I take it for a ride and it seemed WORSE. Like 3 mph off. I am like WTF. I stop at store come back restart Mav drive home and see hey it looks correct . Now but only going 30 mph. I go to highway get up to 60 mph on speedo set cruise look at GPS and its dead on now. So it appears you have to drive once then shut of drive again to have settings take place.

Excellent. (oh - circumference for the search. probably)

Are you in AWD trim?
That seems to be another kicker in several threads.
That module being happy with changes.

I might also suggest - every Service process I've looked at in Forscan Lite - says there must be NO DTC's prior to running the process.

It might be safer to confirm no DTC's in those modules prior to Running anything, like if experimenting already. Maybe afterwards too.

I'd suggest that for others - some of the other threads indicate there is a max change amount, or max limits either direction - and then you'll throw DTC codes.
They seem to point out what those limits are.

 

[Tbone289]

"Master Blaster"
I've never heard of the engineering mode. How do you display it?
Besides tire size, what other perimeters can be changed on it?

https://www.mavericktruckclub.com/f...s-adjustment-via-engineering-test-mode.58342/

 

[deputylynch]

"Master Blaster"
I've never heard of the engineering mode. How do you display it?
Besides tire size, what other perimeters can be changed on it?

AFE has nothing to do with tire sizes affecting the speedometer or odometer.

It's only used to change the fuel mileage calculation on the dash.

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