Forscan
We are lucky to have easy access to settings beyond what you can find in you center consol via a program called Forscan. You'll need an OBD2 to USB adapter as well. There's a slightly learning curve if you've never used Forscan before, so we'll go over the tweaks pertinent to our products. If you haven't already...
Purchase OBD2 Adapter Here (you can find this on Amazon too)
Don't forget to download and install the applicable drivers for whichever OBD2 to USB adapter you get! It won't connect if you don't. On the one linked here, the LED will be red if you don't have the driver installed.
Using Forscan
To make changes such as tire size, you'll need the extended Forscan license. You can obtain a trial run here: Support Request (forscan.org). There are many changes you can make using Forscan beyond just tire size. For example, you can turn off door chimes, couple the grill lights to daytime running lights, and, on some gen 3 Raptors, you can enable glare free headlights. We encourage you to do some research into all the possibilities.
First Things First...
Connect to your vehicle. You'll find the OBD2 port under the dash. Plug the adapter in there and launch Forscan on your computer if you haven't already.
In the bottom left corner of Forscan, you'll see some icons. Click the circled one to connect to your vehicle.
You might see some notifications/prompts as it connects to the vehicle. Just click through as you see fit. Nothing super important. You can name your vehicle in Forscan if you want. It will connect to all the modules and you'll see any DTC's as well.
The Fun Stuff!
All the modules and the various settings within each can be found under the chip icon on the left as shown:
Once in there, to access the settings for a given module, select it and hit the play button in the bottom left corner. For most things, you'll need to select the "as built" option. Module configuration doesn't always get it right. This will pop up a page with a whole bunch of number/letter codes on it. Backup the values before you make changes! I just take a picture of it on my phone, but there's a backup feature within Forscan. For example in HCM, you might see:
When people describe changes here, you'll see things in the format of HCM 734-01-01 xxxx-xx01-xx--. This might seem confusing at first, but it's not so bad. The "x" means don't change that value and the "-" means Forscan will calculate this value for you when you write the changes. So, for this HCM example you would have 0000-0001-013E entered. Kind of a convoluted way to say "only change two entries, but it works.
After you've changed all the entries you need to change, click the "write all" button. You will likely get a pop up about "incorrect checksum". Just ignore it and continue anyway. It'll automatically correct the values it needs to.
Hit the stop button in the bottom left to get back to the point where you can edit other module configurations.
Keep in mind, some changes will require resetting or relearning modules.
Updating Tire Size
After making the jump from 35s to 37s, you'll want to update your tire size using Forscan. Compared to lots of modifications that can be done with Forscan, this is a very easy one! This is for switching to a factory 37 setup. For tire sizes beyond that, see the continued section.
Follow the steps laid out above to get into the as built configuration of the BdyCM. Look for 726-15-02. You will find something like: 5D26-8B52. The change you want to make here is C1xx-xxxx. In the example here, which is off a real truck, the entered data would be C126-8B52. Write the changes and exit out of the module.
Now if you head over to DTC's (vertical menu on the left), you'll notice there's a new DTC in the PCM. This is 100% expected and nothing to be concerned about. Forscan has the ability to correct this. If you got back to where the modules are in the little chip icon, you'll see at the very top there's a PCM option called "module initialization/relearn vehicle data". Select this and hit the play button. Follow the on-screen prompts.
Once the relearn it is complete, head back to DTC's. Clear the DTC in the PCM. Rescan for DTC's and it should be gone. By the way, if you leave your laptop on the center console while doing all this, there's a good chance you'll get a CMR (camera module) DTC because the laptop is obstructing one of the cameras in the cab. Yes, the truck is always trying to watch you.
Ride Height Calibration
After installing anything that changes the ride height of your vehicle, you'll want to recalibrate the ride height sensors to make sure you are getting the best performance possible out of your shocks. This is very easy to do in Forscan.
First, click on the wrench icon in the lefthand menu. This will pop up a long list of things. Look for "VDM Ride Height Calibration". Select this and hit the play button. Follow the on-screen prompts, which will include telling it approximately how much gas you have in the tank. Note that it will tell you to put the vehicle in "Engineering Test mode". It tells you how to do it and it's easy to do, but it's also not 100% necessary. After this you are good to go!
Updating Tire Size Cont.
There is actually more to tire size than what's listed above. The tire size data is distributed across 726-15-01 and 726-15-02. The difference between the factory configuration for the 37 and 35 trucks happens to only be two values. To accurately capture any tire size, 726-15-01 xxxx-xxxx-ABxx and 726-15-02 CD-xx-xxxx is where tire size data is entered. AB and CD are place holders for the values you should enter. Combined, ABCD is the hex value for the circumference of your wheel in millimeters. If you were to put 40's on, your entries would be 726-15-01 xxxx-xxxx-0Cxx and 726-15-02 78xx-xxxx.
You can further fine tune your speedometer beyond this by measuring your speed and updating tire size accordingly. My favorite way is set the cruise control to 60 mph on a long open section of highway and time how long it takes to drive a certain number of miles. To get your updated tire circumference, multiply the current tire circumference by expected time/actual time. Let's say you drive 10 miles. At 60 mph that should be exactly 10 minutes. If it actually takes you 10.5 minutes, then multiply your current tire circumference by 0.952. Convert that to hex, put the new values in Forscan, and your speedometer should be 100% accurate.