Correct your speedometer error - no flash or tune required
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Joined: Oct 2016
Posts: 60
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From: Iowa
Correct your speedometer error - no flash or tune required
So we've finally figured out how to correct speedometer error (if your truck is just off from the factory or you've changed tire sizes.) Thanks to solodogg on the mustang6g forum for figuring out where in the as-built data this info might be stored, even though I'm sure he'll give me all the credit for decoding the way Ford programs tire size in hex.
To do this you will need a laptop running Windows, the free FORScan software with a free extended license, and some sort of ODB reader that works with FORScan. I recommend and use the ODBLink MX: If you use a Bluetooth reader like the ODBLink MX, you'll need to make sure your laptop has Bluetooth or else you'll need to buy a cheap USB Bluetooth dongle.
This is not meant to be a detailed guide on modifying as-built data, there's a lot you can do with it - some that we've figured out and probably more hiding away if you want to try your sleuthing skills. Check out this thread for a complete guide on how to use this software, including how to download it and get an extended license: https://www.f150forum.com/f118/forsc...-truck-348987/
Also check out Livinitup's spreadsheet for other known working mods, like changing your rear-end gear setting, removing the double-honk or enabling fog lights with the high beams on: https://docs.google.com/spreadsheets...730/edit#gid=0
ANYWAY, Ford programs the tire size of the truck on BCM line 726-12-01 for 2015-2020 trucks in the second four-digit block of hex, and (apparently? needs confirmed) 726-15-01 & 726-15-02 in 2021+ F150s. It's stored as the nominal circumference of the driven wheel in millimeters with a revs/mile conversion factor of 96.7%. To save you the trouble of doing a bunch of math and conversions between decimal and hexadecimal, I've come up with a hex calculator that you can use here: https://docs.google.com/spreadsheets...it?usp=sharing
This is covered in a the spreadsheet, but for example my Mustang GT PP currently has this on BCM line 726-12-01:
xxxx 0858 xxxx
If I changed my rear tires to 305/35R19's, my calculated value is this:
xxxx 0843 xxxx
On a 2021+ F150, the value is spread across two addresses like this (NEEDS CONFIRMED):
726-15-01 xxxx xxxx 08xx
726-15-02 43xx xxxx xxxx
The x's mean to leave whatever value is already there.
You also have two options here. You can simply enter the size of your current rear tires as in my example above, and using the nominal diameter of that tire size the calculator will give you a hex value you can program to get pretty close (maybe even dead on) with the speedometer. Tire manufacturers vary of course, and your car's speedometer may be a little weird. So below the tire size calculator is a truing calculator that relies on a precise measurement from GPS. As stated in the calculator, I recommend that you use a GPS that can output in tenths of a mile per hour, that you set the cruise on level ground as high as reasonable (eg 75mph) and that you use the needle rather than the digital speedo or digital cruise setting to set your speed, since the digital outputs are rounded to the nearest whole MPH. Try to set the needle exactly on one of the MPH hash marks on your speedometer for best results.
How to clear P160A DTC: You will need to go into the config section of FORScan and perform a PCM vehicle data relearn. See screenshot here If available in FORScan, you should also do a TCM relearn.
2011-2014 truck owners: your as-built is different. I believe in the last-gen trucks (after the mid-cycle engine upgrade) that the tire size is programmed on BCM line 726-45-01. However, nobody to my knowledge has successfully used this method to recalibrate their speedometer in a 2011-2014. 2014 Raptor example: 726-45-01 xxxx 0A5C xxxx. Also that first block that I've obscured with xxxx's is probably the rear end ratio on the last gen trucks (019A -> 4.10)
FWIW, if you have other Ford vehicles this seems to work on them as well. I don't own an F150, but thanks to Freedom Racing for letting me borrow their shop truck to confirm this and fix the speedometer on it. The exact same BCM line works on Mustangs, for example.
Enjoy your corrected speedometer and welcome to the world of as-built modding.
To do this you will need a laptop running Windows, the free FORScan software with a free extended license, and some sort of ODB reader that works with FORScan. I recommend and use the ODBLink MX: If you use a Bluetooth reader like the ODBLink MX, you'll need to make sure your laptop has Bluetooth or else you'll need to buy a cheap USB Bluetooth dongle.
This is not meant to be a detailed guide on modifying as-built data, there's a lot you can do with it - some that we've figured out and probably more hiding away if you want to try your sleuthing skills. Check out this thread for a complete guide on how to use this software, including how to download it and get an extended license: https://www.f150forum.com/f118/forsc...-truck-348987/
Also check out Livinitup's spreadsheet for other known working mods, like changing your rear-end gear setting, removing the double-honk or enabling fog lights with the high beams on: https://docs.google.com/spreadsheets...730/edit#gid=0
ANYWAY, Ford programs the tire size of the truck on BCM line 726-12-01 for 2015-2020 trucks in the second four-digit block of hex, and (apparently? needs confirmed) 726-15-01 & 726-15-02 in 2021+ F150s. It's stored as the nominal circumference of the driven wheel in millimeters with a revs/mile conversion factor of 96.7%. To save you the trouble of doing a bunch of math and conversions between decimal and hexadecimal, I've come up with a hex calculator that you can use here: https://docs.google.com/spreadsheets...it?usp=sharing
This is covered in a the spreadsheet, but for example my Mustang GT PP currently has this on BCM line 726-12-01:
xxxx 0858 xxxx
If I changed my rear tires to 305/35R19's, my calculated value is this:
xxxx 0843 xxxx
On a 2021+ F150, the value is spread across two addresses like this (NEEDS CONFIRMED):
726-15-01 xxxx xxxx 08xx
726-15-02 43xx xxxx xxxx
The x's mean to leave whatever value is already there.
You also have two options here. You can simply enter the size of your current rear tires as in my example above, and using the nominal diameter of that tire size the calculator will give you a hex value you can program to get pretty close (maybe even dead on) with the speedometer. Tire manufacturers vary of course, and your car's speedometer may be a little weird. So below the tire size calculator is a truing calculator that relies on a precise measurement from GPS. As stated in the calculator, I recommend that you use a GPS that can output in tenths of a mile per hour, that you set the cruise on level ground as high as reasonable (eg 75mph) and that you use the needle rather than the digital speedo or digital cruise setting to set your speed, since the digital outputs are rounded to the nearest whole MPH. Try to set the needle exactly on one of the MPH hash marks on your speedometer for best results.
How to clear P160A DTC: You will need to go into the config section of FORScan and perform a PCM vehicle data relearn. See screenshot here If available in FORScan, you should also do a TCM relearn.
2011-2014 truck owners: your as-built is different. I believe in the last-gen trucks (after the mid-cycle engine upgrade) that the tire size is programmed on BCM line 726-45-01. However, nobody to my knowledge has successfully used this method to recalibrate their speedometer in a 2011-2014. 2014 Raptor example: 726-45-01 xxxx 0A5C xxxx. Also that first block that I've obscured with xxxx's is probably the rear end ratio on the last gen trucks (019A -> 4.10)
FWIW, if you have other Ford vehicles this seems to work on them as well. I don't own an F150, but thanks to Freedom Racing for letting me borrow their shop truck to confirm this and fix the speedometer on it. The exact same BCM line works on Mustangs, for example.
Enjoy your corrected speedometer and welcome to the world of as-built modding.
Last edited by Spart; Jan 26, 2021 at 12:42 PM. Reason: Added 2021+ info
So we've finally figured out how to correct speedometer error (if your truck is just off from the factory or you've changed tire sizes.) Thanks to solodogg on the mustang6g forum for figuring out where in the as-built data this info might be stored, even though I'm sure he'll give me all the credit for decoding the way Ford programs tire size in hex.
To do this you will need a laptop running Windows, the free FORScan software with a free extended license, and some sort of ODB reader that works with FORScan. I recommend and use the ODBLink MX: https://www.amazon.com/dp/B006NZTZLQ If you use a Bluetooth reader like the ODBLink MX, you'll need to make sure your laptop has Bluetooth or else you'll need to buy a cheap USB Bluetooth dongle.
This is not meant to be a detailed guide on modifying as-built data, there's a lot you can do with it - some that we've figured out and probably more hiding away if you want to try your sleuthing skills. Check out this thread for a complete guide on how to use this software, including how to download it and get an extended license: https://www.f150forum.com/f118/forsc...-truck-348987/
Also check out Livinitup's spreadsheet for other known working mods, like changing your rear-end gear setting, removing the double-honk or enabling fog lights with the high beams on: https://docs.google.com/spreadsheets...730/edit#gid=0
ANYWAY, Ford programs the tire size of the truck on BCM line 726-12-01 for 2015+ trucks in the second four-digit block of hex. It's stored as the nominal circumference of the driven wheel in millimeters with a revs/mile conversion factor of 96.7%. To save you the trouble of doing a bunch of math and conversions between decimal and hexadecimal, I've come up with a hex calculator that you can use here: https://docs.google.com/spreadsheets...it?usp=sharing
This is covered in a the spreadsheet, but for example my Mustang GT PP currently has this on BCM line 726-12-01:
xxxx 0858 xx
If I changed my rear tires to 305/35R19's, my calculated value is this:
xxxx 0843 xx
The x's mean to leave whatever value is already there.
2014 and under truck owners: do not despair! I believe in the last-gen trucks that the tire size is programmed on BCM line 726-45-01. Someone will need to test that out and confirm that. Let me know if you have success!
2014 Raptor example: 726-45-01 xxxx 0A5C xxxx. Also that first block that I've obscured with xxxx's is probably the rear end ratio on the last gen trucks (019A -> 4.10)
You also have two options here. You can simply enter the size of your current rear tires as in my example above, and using the nominal diameter of that tire size the calculator will give you a hex value you can program to get pretty close (maybe even dead on) with the speedometer. Tire manufacturers vary of course, and your car's speedometer may be a little weird. So below the tire size calculator is a truing calculator that relies on a precise measurement from GPS. As stated in the calculator, I recommend that you use a GPS that can output in tenths of a mile per hour, that you set the cruise on level ground as high as reasonable (eg 75mph) and that you use the needle rather than the digital speedo or digital cruise setting to set your speed, since the digital outputs are rounded to the nearest whole MPH. Try to set the needle exactly on one of the MPH hash marks on your speedometer for best results.
FWIW, if you have other Ford vehicles this seems to work on them as well. I don't own an F150, but thanks to Freedom Racing for letting me borrow their shop truck to confirm this and fix the speedometer on it. The exact same BCM line works on Mustangs, for example.
Enjoy your corrected speedometer and welcome to the world of as-built modding.
To do this you will need a laptop running Windows, the free FORScan software with a free extended license, and some sort of ODB reader that works with FORScan. I recommend and use the ODBLink MX: https://www.amazon.com/dp/B006NZTZLQ If you use a Bluetooth reader like the ODBLink MX, you'll need to make sure your laptop has Bluetooth or else you'll need to buy a cheap USB Bluetooth dongle.
This is not meant to be a detailed guide on modifying as-built data, there's a lot you can do with it - some that we've figured out and probably more hiding away if you want to try your sleuthing skills. Check out this thread for a complete guide on how to use this software, including how to download it and get an extended license: https://www.f150forum.com/f118/forsc...-truck-348987/
Also check out Livinitup's spreadsheet for other known working mods, like changing your rear-end gear setting, removing the double-honk or enabling fog lights with the high beams on: https://docs.google.com/spreadsheets...730/edit#gid=0
ANYWAY, Ford programs the tire size of the truck on BCM line 726-12-01 for 2015+ trucks in the second four-digit block of hex. It's stored as the nominal circumference of the driven wheel in millimeters with a revs/mile conversion factor of 96.7%. To save you the trouble of doing a bunch of math and conversions between decimal and hexadecimal, I've come up with a hex calculator that you can use here: https://docs.google.com/spreadsheets...it?usp=sharing
This is covered in a the spreadsheet, but for example my Mustang GT PP currently has this on BCM line 726-12-01:
xxxx 0858 xx
If I changed my rear tires to 305/35R19's, my calculated value is this:
xxxx 0843 xx
The x's mean to leave whatever value is already there.
2014 and under truck owners: do not despair! I believe in the last-gen trucks that the tire size is programmed on BCM line 726-45-01. Someone will need to test that out and confirm that. Let me know if you have success!
2014 Raptor example: 726-45-01 xxxx 0A5C xxxx. Also that first block that I've obscured with xxxx's is probably the rear end ratio on the last gen trucks (019A -> 4.10)
You also have two options here. You can simply enter the size of your current rear tires as in my example above, and using the nominal diameter of that tire size the calculator will give you a hex value you can program to get pretty close (maybe even dead on) with the speedometer. Tire manufacturers vary of course, and your car's speedometer may be a little weird. So below the tire size calculator is a truing calculator that relies on a precise measurement from GPS. As stated in the calculator, I recommend that you use a GPS that can output in tenths of a mile per hour, that you set the cruise on level ground as high as reasonable (eg 75mph) and that you use the needle rather than the digital speedo or digital cruise setting to set your speed, since the digital outputs are rounded to the nearest whole MPH. Try to set the needle exactly on one of the MPH hash marks on your speedometer for best results.
FWIW, if you have other Ford vehicles this seems to work on them as well. I don't own an F150, but thanks to Freedom Racing for letting me borrow their shop truck to confirm this and fix the speedometer on it. The exact same BCM line works on Mustangs, for example.
Enjoy your corrected speedometer and welcome to the world of as-built modding.
I thought I had already gained all the value I could out-of Forscan but I guess not - I'm excited to go home and test this out. Will report back with my results. Thanks again.
Senior Member
Joined: Sep 2015
Posts: 893
Likes: 126
From: Richmond,Va
Is the extended license needed for this? Since the extended license is only a trial for a few weeks, I prefer not using it unless needed. I think I read you need it when messing with the PATS?
Thread Starter
Member
Joined: Oct 2016
Posts: 60
Likes: 56
From: Iowa
It's two months, and you can just request a new license. No big deal.
Thread Starter
Member
Joined: Oct 2016
Posts: 60
Likes: 56
From: Iowa
PM me your VIN and I'll see what I can see. Not sure if those trucks work the same way.
ETA: not sure if it can be done. I was looking at the 09-10 trucks, and while they do have as-built data it seems to be quite limited. Much more research would be required to figure out if anything is possible.
ETA: not sure if it can be done. I was looking at the 09-10 trucks, and while they do have as-built data it seems to be quite limited. Much more research would be required to figure out if anything is possible.
Last edited by Spart; Oct 20, 2016 at 03:22 PM.
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Senior Member
Joined: Sep 2015
Posts: 893
Likes: 126
From: Richmond,Va
Oh you can just keep requesting the temporary licenses? Cool didn't know that.