How to: Recalibrate Speedometer with Forscan for 2021 Bronco

[redone17]

Just wanted to give an update that PCM relearn option worked for me today, and NO I did not download the latest version released 04/19/22, I used the previous version 2.3.46 released on 02/07/22, so I am not sure why but it did, it is worth a try, and if it doesn't then perform the PCM service reset function

Question for the experts here, If I ONLY


change the TPMS value in BdyCM but NOT the diameter, do I need to execute PCM and AWD relearn functions again to prevent a PCM 160A DTC??

I changed my tires to 295/70R18 so I increased the TPMS from 35 to 39 (mimicking sasquatch value) and my speedometer is spot on at 2600 circumference, but after checking tiresize.com/pressure-calculator/ it seems I should use the same 35 psi as my stock OBX tires.

Thanks

So interesting to me that the larger tire is suggesting lower PSI. I’ve already been running them around 36-37 due to comfort. Even after reading the disclaimer - it should make sense - but, my brain doesn’t comprehend.

I should do the chalk test.

Is there any difference in changing the TPMS value? The warning doesn’t go off until it’s in the high 20s.

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[cmjuetten]

Thanks for the write up and fix for code 160A, worked as advertised. I guess that’s one advantage of waiting 22 months for your Bronco, most 1st time issues are already resolved.
Just curious did most of the Broncos with the PCM re-learn issue have the non-AWD transfer case like my Black Diamond?

 

[feralc]

[/QUOTE]

So interesting to me that the larger tire is suggesting lower PSI. I’ve already been running them around 36-37 due to comfort. Even after reading the disclaimer - it should make sense - but, my brain doesn’t comprehend.

I should do the chalk test.

Is there any difference in changing the TPMS value? The warning doesn’t go off until it’s in the high 20s.

Your situation is even weirder than mine as both your tires are LT, my stock OBX tire was a regular metric so because I changed to an LT tire it kind of “made sense” to me that I needed the same tire pressure as LT tires (and especially my E rated Ridge Grapplers) have higher load ratings so 35 would be enough. But your case got me wonder because your previous tire is an LT too.
If you do the same comparison using the Goodyears that come with Sasquatch it gives you the same result (35 psi) because supposedly those tires have that max pressure (Tirerack and Goodyear websites confirmed this) so maybe your larger tire has the same situation.

Regarding changing the TPMS value to 35 when it is not really necessary as you pointed it out, that is just my OCD kicking in!!
If I know something is not quite right it just drives me crazy

but you didn’t answer me, do you thinkI need to rerun AWD and PCM relearn processed after changing only TPMS value??
Thanks

 

[feralc]

Thanks for the write up and fix for code 160A, worked as advertised. I guess that’s one advantage of waiting 22 months for your Bronco, most 1st time issues are already resolved.
Just curious did most of the Broncos with the PCM re-learn issue have the non-AWD transfer case like my Black Diamond?

I have an outerbanks and the PCM relearn function worked for me.

 

[feralc]

Happy to report that changing TPMS benchmark does NOT create any DTCs (not even not present/stored ones), only changing diameter of tires does.
And PCM and AWD relearn functions work now, not sure if FORD updated something OTA that allows that to happen.
And my engine is 2.7 though, because I read on this thread that Forscan was having issues unlocking PCM for writing.

 

[Vikingnene]

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...

 

[Tricky Dick]

I am a Mac guy. Seems there is no forscan love for Apple? Have any of you purchased a cheap Windows 10 laptop just for forscan? Any recommendations?

Forscan takes no processing power. I'm using a 15 year old netbook with XP on it.

 

[GRAYFOX-SVT]

So everything has been fine since doing this on mine but even when putting in the new circumference of my tires my speedometer is still off by approx 2 mph. I went from 255/70/18's to 285/70/17's. Is being 2 MPH off make much difference or can you get it exactly where it should be? Any suggestions on what increments to change the circumference to to get it closer if it is worth it?

 

[redone17]

So everything has been fine since doing this on mine but even when putting in the new circumference of my tires my speedometer is still off by approx 2 mph. I went from 255/70/18's to 285/70/17's. Is being 2 MPH off make much difference or can you get it exactly where it should be? Any suggestions on what increments to change the circumference to to get it closer if it is worth it?

I had to decrease the number in increments of 50 and then 20 until it was spot on with Waze and a secondary GPS speedometer that displayed to the tenth of a mile. It’s pretty darn close. I went on the highway at a steady 70MPH using cruise control.

 

[GRAYFOX-SVT]

I had to decrease the number in increments of 50 and then 20 until it was spot on with Waze and a secondary GPS speedometer that displayed to the tenth of a mile. It’s pretty darn close. I went on the highway at a steady 70MPH using cruise control.

I’ll start there and keep making tweaks to lower the circumference and see how close I can get it

 

[pborrica]

Just installed 35s and attempting to adjust the circumference, but running into AWD P160A and ABS U0403 error codes. I followed rtaylor's instructions, but still running into some errors. Anyone have any tips to clear the errors?

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.

 

[22OBX]

Just installed 35s and attempting to adjust the circumference, but running into AWD P160A and ABS U0403 error codes. I followed rtaylor's instructions, but still running into some errors. Anyone have any tips to clear the errors?

May want to clear DTCs and drive it if you followed the procedure

 

[redone17]

Just installed 35s and attempting to adjust the circumference, but running into AWD P160A and ABS U0403 error codes. I followed rtaylor's instructions, but still running into some errors. Anyone have any tips to clear the errors?

You need to hit the button circled below to clear DTC. I kept thinking it was the trash can - but, that just clears the log.

 

[pborrica]

May want to clear DTCs and drive it if you followed the procedure

You need to hit the button circled below to clear DTC. I kept thinking it was the trash can - but, that just clears the log.

Thanks for the responses! If I clear the logs, rerun the read DTC, and don’t come up with any errors then I should be ok?

 

[redone17]

Thanks for the responses! If I clear the logs, rerun the read DTC, and don’t come up with any errors then I should be ok?

Yup!

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