How to: Recalibrate Speedometer with Forscan for 2021 Bronco

[M4Madness]

My Sasquatch tire circumference is listed in Forscan as being 1.2“ shorter than the advertised diameter of the tires. Does anyone know why?

Sasquatch tires aren't true 35".

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[Jhuff]

Sasquatch tires aren't true 35".

True. I believe they are 34.4“ and Forscan says they are 2653mm, which equals 33.25“, which should be the approximate circumference of a bald Sasquatch tire. That's what got me thinking.

 

[M4Madness]

True. I believe they are 34.4“ and Forscan says they are 2653mm, which equals 33.25“. wich should be the approximate circumference of a bald Sasquatch tire. That's what got me thinking.

I figured that you probably knew that, but posted it anyway for anyone who may not. I read somewhere that the Sasquatch tires are actually way under 35" -- something in the upper 33" range -- so what you are saying would confirm that.

 

[WuNgUn]

Use the PCM service function instead of the PCM relearn. The PCM relearn doesn't work.

Detail:
1- I used FORScanSetup2.3.47.test20220221 (version that supports MY2022 goat modes) with OBDLink EX. You will also need a FORScan demo license.
FORScanSetup2.3.47.test20220221.exe

2- Set front/rear TPMS and tire size in BdyCM. For KM3 37x12.50R17D on sasquatch wheels, use 35psi and 2760mm. For sasquatch stock tires and wheels, use 39psi and 2653mm. Tire circumference cannot exceed 2800mm. DTC's will be set in 2-3 modules that will need to be fixed.

3 - To fix the non-PCM DTC's, run the AWD relearn. Don't run the PCM relearn (it doesn't work).

4 - Clear the DTC's. All should be cleared except PCM.
5 - Run the PCM reset-all-adaptations service function. This will fix the size mismatch and also clear the PCM DTC. It will relearn the engine/trans/fuel adaptations over time while driving.

6 - Confirm all DTCs are cleared.

7 - Install a free speedometer app with tenth-mph readout on your phone and testdrive to confirm speed is within 0.5mph at 60mph cruise control. For new tires, the actual speed should be a little higher than speedo. For worn tires the actual speed will be a little less.

Is 2653mm the circumference I want to use to fix the 2Km/h error with stock Sasquatch tires as it comes from the factory?
Thanks

 

[Jhuff]

Is 2653mm the circumference I want to use to fix the 2Km/h error with stock Sasquatch tires as it comes from the factory?
Thanks

That's the number that Sasquatch came with from the factory. It will never stay perfect, unless you continuously play with the numbers as the tires wear.

 

[WuNgUn]

That's the number that Sasquatch came with from the factory. It will never stay perfect, unless you continuously play with the numbers as the tires wear.

Yeah, I understand about the wear...
I just don't want a 2% difference right NOW
Lol

 

[‘21OBX]

I believe someone has stated you have to measure from the center of the rim to the ground with the tire mounted on vehicle and vehicle on the ground to get the proper measurements. As it is going to be different then a non load bearing tire. Also one close I just kept changing it slowly until it was dang close to two gos Speedo apps on my phone.

 

[WuNgUn]

I believe someone has stated you have to measure from the center of the rim to the ground with the tire mounted on vehicle and vehicle in the ground to get the proper measurements. As it is going to be different then a non load bearing tire. Also one close I just kept changing it slowly until it was dang close to two gos Speedo apps on my phone.

So, center of tire to the ground to get the radius, determine the diameter from that and then calculate the circumference? Lol
I think I'll just change it but by bit like you did.

 

[shawn6107]

Just make sure after you change the tire size to force the TCM and PCM to relearn and do the reset of the DTC, then you should not have any error messages:

13. Now we have discrepancy between tire size values known by PCM and TCM and new value stored in BdyCM. So we have P160A DTC in TCM module and P0610 in PCM module:

14. In order to remove the discrepancy, we need to force PCM and TCM to “learn” the new value from the ECC. We can do it using Module Initialization/Relearn vehicle data functions for PCM and TCM module:

Note: some cars may have other modules that require this operation, for example AWD, SOBDMC.

15. After running the Relearn functions, we need to reset the DTCs:

Mine won’t run the PCM relearn. As soon as it sees the different settings in the BdyCM, it stops the service. However, no codes thrown as of yet and I’ve driven it several times since I made the change.

 

[redone17]

Mine won’t run the PCM relearn. As soon as it sees the different settings in the BdyCM, it stops the service. However, no codes thrown as of yet and I’ve driven it several times since I made the change.

Make sure you use the second button from left to clear DTCs. Not the trash can. I made that mistake at first.

 

[shawn6107]

https://www.bronco6g.com/forum/thre...ter-with-forscan-for-2021-bronco.23064/page-8 read what rtaylor said. Follow it to a T and you will have no problems.

Thanks! I’ll give it a try this weekend when I get back home.

 

[rtazz17]

Use the PCM service function instead of the PCM relearn. The PCM relearn doesn't work.

Detail:
1- I used FORScanSetup2.3.47.test20220221 (version that supports MY2022 goat modes) with OBDLink EX. You will also need a FORScan demo license.
FORScanSetup2.3.47.test20220221.exe

2- Set front/rear TPMS and tire size in BdyCM. For KM3 37x12.50R17D on sasquatch wheels, use 35psi and 2760mm. For sasquatch stock tires and wheels, use 39psi and 2653mm. Tire circumference cannot exceed 2800mm. DTC's will be set in 2-3 modules that will need to be fixed.

3 - To fix the non-PCM DTC's, run the AWD relearn. Don't run the PCM relearn (it doesn't work).

4 - Clear the DTC's. All should be cleared except PCM.
5 - Run the PCM reset-all-adaptations service function. This will fix the size mismatch and also clear the PCM DTC. It will relearn the engine/trans/fuel adaptations over time while driving.

6 - Confirm all DTCs are cleared.

7 - Install a free speedometer app with tenth-mph readout on your phone and testdrive to confirm speed is within 0.5mph at 60mph cruise control. For new tires, the actual speed should be a little higher than speedo. For worn tires the actual speed will be a little less.

THANK YOU for posting this. It got rid of my dtc’s which were driving my ocd“s crazy! For the record I nearly puked when I saw the on screen dtc’s when I changed my tire sizing. First thing I thought was my wife was going to tell me I told You not to mess with it.

 

[Spchgexo]

Wow. You may have solved everyone’s trouble. Provided the dealer knows what they are doing. And will do it.

Lastest .48 for scan version fixes the pcm relearn problem

 

[boomboomthump]

Not for me. The .48 does not work and I get the same error that everyone else in this thread did. Performing the PCM relearn quits and 2% and fails.

I had to perform the other step mentioned a few pages back "PCM reset all adaptations". That allowed the DTC to be cleared.

 

[andersman02]

Followed taylors recent how to and worked perfect first try.

BTW, best way to get the perfect # to use is as someone mentioned above,take a stock reading of where your speedo is at and what your gps says, mine was speed-65, gps 68.

68/65 and multiply your current wheel size by that amount. worked perfect for me

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