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Re: How to use FORScan to adjust tire size

Posted: Wed May 05, 2021 11:15 am
by abagoz
Tire Circumference change fixed my Speedo accuracy. Checked it with a SPEEDO app and Waze. Perfect at 80mph.

Re: How to use FORScan to adjust tire size

Posted: Thu May 20, 2021 12:39 pm
by TX_Jax
Okay, I don't get it. I am running the latest FORScan v2.3.40 beta.

I have a 1999 F350 Superduty

When I click on the item, I get drop down menus. I choose the correct item, but it won't write.

Re: How to use FORScan to adjust tire size

Posted: Thu May 20, 2021 2:31 pm
by TX_Jax
This is what the v2.3.40 does. You choose the right tire size - mine is 657.

Tire Selection Choices 2021-05-20 060447.jpg
Tire Selection Choices 2021-05-20 060447.jpg (179.41 KiB) Viewed 1489 times

Re: How to use FORScan to adjust tire size

Posted: Thu May 20, 2021 2:32 pm
by TX_Jax
And this is what I get when choosing off the menu. I click "Write", then . . .

Writing to GEM 1 Notation 2021-05-19 143849.jpg
Writing to GEM 1 Notation 2021-05-19 143849.jpg (79 KiB) Viewed 1489 times

Re: How to use FORScan to adjust tire size

Posted: Sat May 22, 2021 9:03 pm
by rbentnail
I found the options for pre-2015 vehicles to be pretty scarce. On a vehicle that old you may not be able to do much at all with Forscan. You might consider looking for an add-on aftermarket module.

Re: How to use FORScan to adjust tire size

Posted: Fri Jul 09, 2021 12:36 am
by alzev
I have followed this and every other link related to properly updating my tire size. I have 2021 f150 lariat power post and can’t seem to get it dialed in. I downloaded the spreadsheet that someone had spent a lot of time making and plugged in my numbers and can’t seem to find the two line items that I need to change the algorithm anywhere? Right now I was able to just goto the bodycm and change the diameter based off the above tire calculator and that took me from being 4-5 mph slower to 4-5mph faster. Can someone please point me to the right direction to update the algorithm 726-xxx or what is the proper way to do incremental changes so I can get my system dialed in properly. Any help would be great. Thanks

Re: How to use FORScan to adjust tire size

Posted: Sun Jul 11, 2021 9:54 am
by Erik.p
Great article. thank for this info

Re: How to use FORScan to adjust tire size

Posted: Tue Jul 13, 2021 3:53 pm
by jbroad
For those of you with a 2017-2020 F150 (with 10 speed transmission) and are having DTC errors after writing your tire circumference. I've done quite a bit of research on this and did some extensive testing today. Here are my results:
Capture.PNG
Capture.PNG (51.41 KiB) Viewed 447 times
After attempt #15 I stopped and took the truck for a drive. The speedometer is off about -2.5mph at 70mpg. Actual variance reported on my phone with GPS was fluctuating between 2.3-3.1mph. It's also noteworthy that I did not have to do a DTC reset after a PCM relearn for the attempts with no DTC error.

History
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Before these 15 attempts I tried programming my speedometer with mixed results. I tried the true circumference of my new tires (2718mm) and received DTC error (not visible on dash) which I wasn't happy about. I left it because my speedometer was off just a touch. I ended up changing it to a number that I saw on these forums 2645 (or something like that) that somebody else tried with no DTC error then my speedometer was showing me faster than my GPS which was really odd. During this attempt I still had a DTC error which is what caused me to do so much research that resulted in the 15 attempts I just posted.

Thoughts
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My research has shown absolutely no patterns to why some people with 2017-2020 F150s are getting DTC errors and some people aren't. It makes no sense to me why the maximum value I can program is 2501. I suspect that if I were to change the axle ratio I could set higher than 2501 but I do not want to do that. It's also possible that there is a bug in the version of FORscan that I'm using; possibly with a new revision my results will be different.
My speedometer was off -5mph but now its only off -2.5mph without any DTCs. I guess I'm happy with this unless somebody else has any other ideas.

Re: How to use FORScan to adjust tire size

Posted: Mon Jul 19, 2021 1:22 am
by tidelvr210
boboch wrote:
Sun Mar 21, 2021 10:06 pm
I have a 2015 f150 and change circumference in mm. I do not have a TCM to reset at all to reset. I had the relearn for the PCM did that completed successfully, then reset the DTC successfully all DTC come back with none but the PCM. U0422 invalid data from the body control module. Has anyone come across this problem? Any help would greatly be appreciated.
I have a 2015 F150 Lariat 4x4 Eco FX4 and having basically the same issue. I put Raptor wheels/tires on the truck after a leveling kit. Truck has been 5 MPH off since new, and factory Syc 2 Navi has never been an issue. I just changed to a Sync 3 w/Navi so that I could get Apple Car Play and everything went crazy related to Nav and trying to use Waze on car play. Navi and Apple car play has me way faster than vehicle is going. I adjusted tire size but get the same code. I began a trial and error session and found that I could only adjust tire Circum up to 2532 without getting the error code that would reset. Truck is still 2-3 MPH off vs GPS. In the end, I had to unplug GPS for navi and just use Apple Car play which now works fine without GPS plugged in. Thus, I still can't get Speedo accurate and no factory Navi at this point. Hopeful a work around can be found at some point so that GPS and Speedo can be used without error codes.

Re: How to use FORScan to adjust tire size

Posted: Mon Jul 19, 2021 11:11 pm
by kibosh
I figured I'd add my findings . . . I have a 2020 5L 10 speed Lariat and for some reason I am able to program my tires to 2530 max without a DTC. I should be at about 2550 so I am off by about 1/2 MPH.