FORScan forum

Trying to recalibrate speedo on Fiesta 2014 1.0 EcoBoost.
I write new tire size and circumference in BCM backup then Write to main but cannot see any changes in BCM As built. IPC is showing new data but speedo is still off.

My BCM values in fields from Calculator from first post don't seem valid for tire circumference:

726-12-01 0000 0000 0040

726-15-01 FFFF FFFF FF3E
726-15-02 FFFF FFFF FF3F

Any advices?

You had better check out BCM 726-45-01 here: https://docs.google.com/spreadsheets/d/ ... 1329872825

726-12-01 is for newer vehicles staring in 2015 like my 2015 Lincoln MKC. The middle or second set of figures is where you enter your values. There is a place to enter tire circumference in the newer Forscans and once you change that to your calculated circumference in cm, that will make the changes to your 726-45-01 or 726-12-01 - depending on the age of your vehicle. It's a lot simpler just to enter the tire circumference and hit write. Look in either the BCM or IPC (not asbuilt) it's there somewhere. After that you can do the relearn.

On Fiesta BCM modules go up to 726-16-03
I've changed Tire size and circumference in BCM backup (that one has dropdown menus), wrote it and then wrote to main (Write to main or some command like that). I can see new values in IPC but no value has changed in BCM As Built (I've compared all values before and after)





My dial speedo is about 10% off which is a lot, but digital one available in Test menu (pressing trip reset before ignition on) is spot on.

Calculate your 4 figures of the tire circumference in cm in this calculator conversion and then look for a 4 figure that is the same or similar in the middle 4 numbers. That may lead you to the line for speedo correction where the hex numbers could be entered. In my MKC the decimal 2174 cm calculates to hex 087E and that comes up as 726-12-01 xxxx 087E xxxx. Originally I was 0862. This corrected my speedo.
https://www.binaryhexconverter.com/deci ... -converter

Thanks for suggestion. I've set tire size to 195/55 R15 which equates to 1869mm circumference.
Only value close to that in BCM As Built is at 726-13-07, when converted to decimal it is 1870. But nothing close to circumference which was originally 1760mm (6E0 in hex) which I've changed to 1820mm (71C hex).

Strange thing I've noticed today is that speedo error is practically the same at 60km/h as at 120km/h, around 5-6 km/h. So it behaves like there is factory offset set not like tire size issue which should give same % at various speeds.

The one that look like a tire setting is 726-10-03 xxxx 07E0 xxxx. The 71C you are getting should be 071C - you need the 0 at the beginning. 07E0 calculates to 2016 decimal. 071C calculates to 1820. There is a relearn in Forscan for various modules, try that. The difference from 1870 to 1820 seems to be valid range for speedo correction. I had to go from 2146 cm decimal to 2174 cm decimal to correct mine. My speedo was showing higher than my actual speed. Are you going faster than your speedo shows? I had to increase my 2146 as I was going slower than speedo.

I've omitted leading zeros, sorry about that. Since 07E0 (2016 decimal) is larger than 1820, speedo should be showing higher speed than actual, not lower. And size difference is too big, Fiesta cannot take 2016mm tire, so I doubt it's that one.

EDIT: Any idea what Instrument cluster calibration is?

You are correct, I made error with the 1870 figure - don't know where I got that one.

I don't see anything in my ICM that would correlate with tire setting. There may be but I just don't know. There might be some setting for wheel ticks which measure speed as well I would research the ABS and transmission modules to see if you can find anything that way. In my 06 Mustang GT it's a lot easier as with my SCT tuner I just set the rear end axle ratio and revs per mile and that does everything. In the 2015 Lincoln MKC it was tougher and took a much longer time to determine.

I tried about 20 times today to configure a new tire size in my 2019 F150, and I'm not having any luck. I've tried multiple sizes, I tried adjusting the values directly in 726-12-01 using multiple different known good values and values from the spreadhseet tool, and I tried changing the tire circumference. In every instance, I used the relearn function for both the PCM and TCM, but stull get a U0422 error in the PCM. I switch it back to stock and use the relearn function and the error code is gone and everything is fine. I can't figure out what I'm doing wrong. These are the steps I've been following:

1. Launch Forscan and connect to truck with ignition on, but truck not running.
2. Click on the Chip icon.
3. Click on "BdyCM (AS BUILT format)"
4. Click on the Play icon on the bottom.
5. Enter values for ABCD in 726-12-01 XXXX ABCD XXXX
6. Click "Write"
7. Turn ignition of and back on and click "ok" in the prompt
8. Click on the stop button, aka "Stop Service Procedure" button
9. Click on "PCM Module initialization/relearn vehicle data"
10. Turn ignition off when prompted, click "ok"
11. Turn ignition on but don't start the vehicle when prompted, click "ok"
12. Click on "TCM Module initialization/relearn vehicle data"
13. Turn ignition off when prompted, click "ok"
14. Turn ignition on but don't start the vehicle when prompted, click "ok"

At this point I'm still getting the PCM error code, even if I rest the DTCs and check them again.

I also tried the following:

3. Click on "BdyCM"
4. Click on the Play icon on the bottom.
5. Find the entry for Tire Circumference and enter in the new value
6. Click "Write"
7. Turn ignition of and back on and click "ok" in the prompt
8. Click on the stop button, aka "Stop Service Procedure" button
9. Click on "PCM Module initialization/relearn vehicle data"
10. Turn ignition off when prompted, click "ok"
11. Turn ignition on but don't start the vehicle when prompted, click "ok"
12. Click on "TCM Module initialization/relearn vehicle data"
13. Turn ignition off when prompted, click "ok"
14. Turn ignition on but don't start the vehicle when prompted, click "ok"

I get the same error code using this method.

Any ideas?