How to: Recalibrate Speedometer with Forscan for 2021 Bronco

[hammsammich]

I want to thank rtaylor for posting the PCM procedure. I was able to relearn the AWD but as other said I couldn't relearn the PCM. I just figured I'd drive it with the code since it wasn't showing the light and everything else was operating fine. Until I had to take it on a 3 hr drive this morning and the cruise control wouldn't work. I read this thread and reset the PCM and everything is working again and now my speedo is dead on. Much appreciated.

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[RustysBronco]

@Moderator can we make this thread sticky? Tons of useful info here.

 

[BigMeatsBronco]

I just posted this on the Transmission, Axles, Gears area, but feel this thread is hitting a lot of the notes of what I am dealing with. Hopefully someone has some valuable feedback...


Gentlemen,
New to the forum and was hoping I could find some answers. I blazed a trail not knowing what I would come up against, but here is where I am at and what I know so far: I have a 2021 Bronco 2-Door Base manual trans. I won't go into all the mods, but where I have run into issues with the electronics is with tire size and with axle ratio. I've got a set of 37" tires on there and they were causing my tranction control system to freak out, especially on tight turns. Keep in mind this is not because they are 37" tires, as many of you have been running them without any perceivable issues, but that is because most people upgrading to 37" tires are coming from 35" tires and the change is not enough for you to notice the traction control system being a little more sensative. When you go from 30" tires to the 37" tires, however, you notice it. A lot! Any tight turn, even out of a parking spot, and it starts grabbing brake. Hook it up to FDRS and record what is going on and you find it does not like the calculations between the inside and outside tires during a turn, as the circumference of the tires come in to play in the non-linear equation. This is fairly easily resolved with ForScan as long as that is the only mod you have done. But, in the case of my little 2-Door, I swapped out the axles with Ford Performance axles front and rear. The rear axle is a simple one (M220 to M220) but the front one gave me a few challenges. Going M190 to M210 is something that can be done, but you have to read the fine print now available (not available when I ordered my front diff last June) that states you have to order the front M210 diff with the 4.46 gears if you are converting from an M190 diff. It turns out that the 4.46 version uses a different ring carrier that works with the passenger side axle shaft from the M190 diff., but the 4.70 version is offset and does not allow the axle shaft to seat all the way in to the center carrier without bottoming out on the pins. Time to machine the factory M190 axle shaft, of course! After that was done and all the parts fit together properly, it was time to re-gear the front and rear axles. As many of you know, there are no gear sets available for these, so when I found a combination of gears/bearing/seals/crush sleeves that worked back in February, I was ecstatic! Install the axles with the new 5.38 gears and I am almost 100% back to my original gear ratio with the 30" tires and the 4.46 gears. Enter the electronic nightmare!!! I have been battling this for quite some time now and this is where I have gotten to: The BCM (Body Control Module) will reprogram (using ForScan) to the 5.38 gears. From there, the AWD module and the PCM both freak out, so you have to program them as well. Easier said than done... The AWD module is fairly simple, as you can tell it to relearn it's parameters from the BCM and all should be good. The PCM, however, is not happy. I theory it works the same way as the AWD module for a relearn, but it errors out saying the new axle ratio is outside parameters allowed. And without the PCM onboard with the other modules and them being on the same network, the AWD receives contradicting signals from the PCM compared to the BCM and throws a code and the PCM throws a code for having a different value than the BCM. For the icing on the cake, it allows you to drive normal for a short period of time and then puts you into limp mode (i.e. very limited throttle and no boost, to the tune of flat out on the freeway at 50mph). Makes for a very interesting drive! Now, you can pull over, turn off the vehicle, let it reset and then start in on your journey again only to have it repeat that 3-6 miles later depending on how you drive (I have found it to be RPM dependent). I know it took me a long time to get to this question, but does anyone know what the parameters are for the PCM (Power Control Module) as far as axle ratios are concerned? And if not, is there a work around for this issue? A way to fool the modules? The transmission output shaft sensor is obviously not happy with the calculations when compared to the axle shaft sensors (wheel speed sensors). Any and all information would be appreciated. I'm at the end of my rope and really would prefer not to pull the axles back out only to re-gear them again with the factory 4.70 gears (which I only assume are within specs for the PCM). Someone please have a cool hack for this...

Ford is working on a fix right now and hopefully it will be released next month with the Spicer 5.38 gear sets that are being released. I'm also going to go with 5.38 s very soon. Keep us posted on your outcome.

 

[603BB]

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.

Just followed this process today (FORScan Setup 2.3.48). Worked perfect to eliminate my "Check 4x4" and "Service Vehicle Soon" warnings.

Thank you rtaylor for the snapshots as well.

 

[iwantabasebronco]

Reporting a successful circumference change today. Downloaded forscan this AM (so whatever version that is newest). No codes after PCM and AWD relearn (yes- successful pcm relearn!) I will note that my base showed fewer modules than some higher trim examples shown here(maybe I’m reading something wrong?). I do not have AWD option, just 4x4. Big bend wheels and tires on base with 2.7L.

Drove so Speedo read 60 and Waze read 64. So 1.066667 was my conversion factor. Circumference value I entered in forscan was 2474. I’m now dead nuts on at all speeds (only tested up to 70). Will follow up if I get any lights in the coming days.
Thank you all for providing instructions on this process.

 

[BenBronco]

• 1

Just wondering if anybody has tried to calibrate there speedo with Forscan. I did mine and when I changed my tire circumference to proper size i went from reading under to over my actual speed and lost my cruise control. I have the 2.3L with a manual transmission so I’m just wondering if anyone has a solution for this.

I have the same problem.

 

[BWepps]

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 test drive 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 @rtaylor . This cleared my DTC error code on PCM!!

 

[Marshhunt]

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.

Worked perfect. Thanks!

 

[Debc]

Ok did all that it is now 2 miles faster the other number i used 2618 was closer but i guess if i change it i have to go threw all that again ? With speedo 2 miles hr faster guess it stops speeding tickets

 

[TeocaliMG]

Hey Guys, a little late to the party. Just threw 37's on the badlands and am starting to experience some of these issues. I noticed that the programmed tire size was 31.6" (badlands came with 33's) so unsurprisingly when I put the true diameter in for my 37's the speed was off by about 5% (about the delta that the preprogrammed size was off. I have gotten the speed dialed in, but noticed that cruise control drops out basically every time I try it, and will stay off until the next key cycle. I will try clearing codes next time I am out, but don't have high confidence that will properly solve the issue. Any ideas? Something to do with engine load/RPM/Speed that is interrupting CC?

Edit: I seem to have cruise control now. I cleared DTC's but I think the main thing is I disabled TPMS. I set up my new tires (Beadlock) without TPMS because I wanted both sets of tires accessible and its a chore to get the old TPMS out. I think the TPMS absent was inhibiting cruise, maybe some safety thing i was unaware of. I will eventually set up TPMS on the new set.

 

[Debc]

Hey Guys, a little late to the party. Just threw 37's on the badlands and am starting to experience some of these issues. I noticed that the programmed tire size was 31.6" (badlands came with 33's) so unsurprisingly when I put the true diameter in for my 37's the speed was off by about 5% (about the delta that the preprogrammed size was off. I have gotten the speed dialed in, but noticed that cruise control drops out basically every time I try it, and will stay off until the next key cycle. I will try clearing codes next time I am out, but don't have high confidence that will properly solve the issue. Any ideas? Something to do with engine load/RPM/Speed that is interrupting CC?

Edit: I seem to have cruise control now. I cleared DTC's but I think the main thing is I disabled TPMS. I set up my new tires (Beadlock) without TPMS because I wanted both sets of tires accessible and its a chore to get the old TPMS out. I think the TPMS absent was inhibiting cruise, maybe some safety thing i was unaware of. I will eventually set up TPMS on the new set.

No the cruise thing was a problem for me too and i keep tpms . Its a prosses of clearing things out to get it back . I just keeping mine at the 2miles off . I am using the stock sas numbers so it may truley not off i havent seen a speed board yet lol

 

[TeocaliMG]

That fix was only partial, if at all. It turns out I only have cruise in gears 1-4, 5 and 6 dont work, 5 might sometimes work below 60 but usually quits. I think it has to do with the PCM/TCM reset, so I will try that and report back.

Edit: SOLVED.
I followed this thread: https://www.bronco6g.com/forum/thre...th-forscan-for-2021-bronco.23064/#post-817418

Post #10 specifically. Its a good start and may work for you. But for me, the PCM relearn did not take. The AWD relearn would take however. My log looked like this:

I tried several thing including restarting my computer and relaunching Forscan. Ultimately I just explored other sections and tried the "PCM Reset All Adaptations" The description was a good fit, and that seemed to work. Did ABS and AWD for good measure as well.

I was able to clear the PCM DTC (probably the root issue) but the ABS and AWD DTC's are still present. My cruise control however now works in 5th and 6th gear and over 70mph.

 

[Twistedbrilliance]

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.

This is great, it worked for me also!! Thanks, I hate having warning lights on.

 

[Mark Borgmann]

Thank you @rtaylor . This cleared my DTC error code on PCM!!

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.

 

[Mark Borgmann]

Thanks Alot that was helpful Dtc cleared

Why would there be a max tire size? Guess putting 38's on will just always be off...

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