How to use FORScan to adjust tire size
Posted: Tue Nov 24, 2020 4:11 am
If vehicle tyres have been changed to another size, vehicle configuration has to be adjusted to keep speedometer readings correct. The change is quite simple, but has few nuances so here is a detailed step by step instruction for this process.
WARNING: Modifying configuration parameters in Module Configuration (As Built format) function and using As Built spreadsheets is not a recommended way. Configuration layout may be different between models/years and using wrong layout may cause problems. Recommended way is to use Module Configuration that lists configuration parameter in a human friendly way. This manual explains how to do it on example of Tire Size.
Note 1: this article is actual for new vehicles with so called Economized Central Configuration (ECC). ECC means that some memory blocks in BdyCM module of the car are reserved to store parameters that are used by several modules. Tire Size is one of such parameters. Although it has been stored in BdyCM, it is actually used by PCM, TCM, AWD, ABS etc. There is some specific in managing ECC, reviewed below.
Note 2: Tire size is programmed as tire circumference in mm. You need to use any tire size calculator to convert from normal tire size to circumference in mm. For example, this one:
https://tiresize.com/calculator/
WARNING: Modifying configuration parameters in Module Configuration (As Built format) function and using As Built spreadsheets is not a recommended way. Configuration layout may be different between models/years and using wrong layout may cause problems. Recommended way is to use Module Configuration that lists configuration parameter in a human friendly way. This manual explains how to do it on example of Tyre Size.
1. Obtain an adapter that works with Ford. We recommend OBDLink EX and vLinker FS.
2. Download FORScan for Windows from our official site:
https://forscan.org/download.html
3. Install Extended License:
https://forscan.org/forum/viewtopic.php?f=5&t=18697
4. Setup the adapter (should be done automatically by Windows)
5. Connect to the vehicle.
6. Go to Configuration and Programming and run BdyCM Module Configuration
7. FORScan will open the list of all configuration parameters available for the BdyCM module:
8. Number of parameters is quite significant, it may be hard to find necessary one. So please use the filter field at the top of the work area to filter the list by key word 'tire':
9. Select the “Tire Circumference” parameter in the table and open the edit dialog box either by clicking twice with left mouse button on the parameter, or by pressing "Edit selected" button:
10. Change the value as you need:
and press OK button.
11. Press Write to write the changed parameter to ECU:
12. FORScan will ask to confirm the change:
Press OK to confirm.
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:
Note: some modules have a harcoded range (min…max) for the tire size. So if new value is out of the range, module will not learn it but throw P1635, U0422 or similar DTC. Unfortunately, in such cases we have no choice other than adjust the new size to be in the range (so, find maximum circumference accepted by the module).
WARNING: Modifying configuration parameters in Module Configuration (As Built format) function and using As Built spreadsheets is not a recommended way. Configuration layout may be different between models/years and using wrong layout may cause problems. Recommended way is to use Module Configuration that lists configuration parameter in a human friendly way. This manual explains how to do it on example of Tire Size.
Note 1: this article is actual for new vehicles with so called Economized Central Configuration (ECC). ECC means that some memory blocks in BdyCM module of the car are reserved to store parameters that are used by several modules. Tire Size is one of such parameters. Although it has been stored in BdyCM, it is actually used by PCM, TCM, AWD, ABS etc. There is some specific in managing ECC, reviewed below.
Note 2: Tire size is programmed as tire circumference in mm. You need to use any tire size calculator to convert from normal tire size to circumference in mm. For example, this one:
https://tiresize.com/calculator/
WARNING: Modifying configuration parameters in Module Configuration (As Built format) function and using As Built spreadsheets is not a recommended way. Configuration layout may be different between models/years and using wrong layout may cause problems. Recommended way is to use Module Configuration that lists configuration parameter in a human friendly way. This manual explains how to do it on example of Tyre Size.
1. Obtain an adapter that works with Ford. We recommend OBDLink EX and vLinker FS.
2. Download FORScan for Windows from our official site:
https://forscan.org/download.html
3. Install Extended License:
https://forscan.org/forum/viewtopic.php?f=5&t=18697
4. Setup the adapter (should be done automatically by Windows)
5. Connect to the vehicle.
6. Go to Configuration and Programming and run BdyCM Module Configuration
7. FORScan will open the list of all configuration parameters available for the BdyCM module:
8. Number of parameters is quite significant, it may be hard to find necessary one. So please use the filter field at the top of the work area to filter the list by key word 'tire':
9. Select the “Tire Circumference” parameter in the table and open the edit dialog box either by clicking twice with left mouse button on the parameter, or by pressing "Edit selected" button:
10. Change the value as you need:
and press OK button.
11. Press Write to write the changed parameter to ECU:
12. FORScan will ask to confirm the change:
Press OK to confirm.
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:
Note: some modules have a harcoded range (min…max) for the tire size. So if new value is out of the range, module will not learn it but throw P1635, U0422 or similar DTC. Unfortunately, in such cases we have no choice other than adjust the new size to be in the range (so, find maximum circumference accepted by the module).
