AlfaOBD help

[Porkking]

Working on my 20 ram, trying to get parking sensors going. Updated my tire size and went over to the dynamic tire circumference programmed it to 2760 mm but checked the value and it’s saying I’m set at 51260mm. Did I miss a step somewhere? Also truck seemed to spaz out on my way home. Dash and shifter when crazy. Shut the truck off then couldn’t get it started. Push to start wouldn’t light up Had to unplug my security bypass and put stick plugs back ti get it going. Ended up setting U0402 code. Any help will be great!!!

 

[boogielander]

what size tire you have? if it's 35x12.5R17 then just use the toyo 35x12.5R17, even if you're not running toyo.

 

[Porkking]

285/65/20 I think I’m good on my sizing input. It’s just that dynamic tire circumference setting doesn’t make sense.

 

[HSKR R/T]

285/65/20 I think I’m good on my sizing input. It’s just that dynamic tire circumference setting doesn’t make sense.

If you use the tire size change option, then you don't mess with dynamic tie circumference.

 

[Porkking]

Unfortunately already did. I was using the information I found on this forum but see it was unnecessary. But u now I can revert to stock because any value I put in, it’s inflating the value

 

[HSKR R/T]

Unfortunately already did. I was using the information I found on this forum but see it was unnecessary. But u now I can revert to stock because any value I put in, it’s inflating the value

I've ran into issues on a friend's truck trying to change the dynamic circumference value and killing the park sensors, ESP, and ABS, and it took a lot of playing seound to get it cleared.

 

[Jimmy07]

Working on my 20 ram, trying to get parking sensors going. Updated my tire size and went over to the dynamic tire circumference programmed it to 2760 mm but checked the value and it’s saying I’m set at 51260mm. Did I miss a step somewhere? Also truck seemed to spaz out on my way home. Dash and shifter when crazy. Shut the truck off then couldn’t get it started. Push to start wouldn’t light up Had to unplug my security bypass and put stick plugs back ti get it going. Ended up setting U0402 code. Any help will be great!!!

The “program tire size” section is a shortcut to “VehConfig 4: Dynamic Tire Circumference”.
When you make a size change in program tire size, that VehConfig 4 value is what is being changed in the BCM.
All of those tires in the list are just shortcut values that the developer converted on his own using those tires’ “on paper” sizes, and most will be inaccurate (yes, I understand that there are some that people have used that have worked for them).

The easiest way to get close right off the bat is to just measure the tire on the truck from the ground to the center of hub in inches x 2 x 3.14 x 25.4 = circumference in mm. Then enter that in either program tire size, or VehConfig 4, doesn’t matter.

As far as the “inflated value” that it’s spitting out, there’s some kind of conversion error that the developer has going on with the current app software version, but as far as what is actually being written to the BCM, it is the 2760 value that you wrote in.
You can verify this by clicking on the battery icon in the lower right, click read system ID, let the list fully populate, and scroll down to VehConfig 4, and you will see that it really is set to 2760.

If you are checking your actual speed vs the speedometer using a gps app on your phone, make sure that your phone is not connected to the truck in any way.

 

[Porkking]

That’s great to hear. I’ll definitely check out the configuration after just doing the “program tire size” I actually sat down and did the math last night and will probably enter that to see if I could fix the parking sensors. That’s what it started me on this whole journey not too concerned about my speed, but would love to have the sensors working.

 

[boogielander]

The “program tire size” section is a shortcut to “VehConfig 4: Dynamic Tire Circumference”.
When you make a size change in program tire size, that VehConfig 4 value is what is being changed in the BCM.
All of those tires in the list are just shortcut values that the developer converted on his own using those tires’ “on paper” sizes, and most will be inaccurate (yes, I understand that there are some that people have used that have worked for them).

The easiest way to get close right off the bat is to just measure the tire on the truck from the ground to the center of hub in inches x 2 x 3.14 x 25.4 = circumference in mm. Then enter that in either program tire size, or VehConfig 4, doesn’t matter.

As far as the “inflated value” that it’s spitting out, there’s some kind of conversion error that the developer has going on with the current app software version, but as far as what is actually being written to the BCM, it is the 2760 value that you wrote in.
You can verify this by clicking on the battery icon in the lower right, click read system ID, let the list fully populate, and scroll down to VehConfig 4, and you will see that it really is set to 2760.

If you are checking your actual speed vs the speedometer using a gps app on your phone, make sure that your phone is not connected to the truck in any way.

yeap the shortcuts are probably inaccurate in my case: Falken Wildpeak AT3W vs Toyo Open Country AT but after comparing with gps app on the phone the difference is not big enough for me to actually sit down and do the math lol