I recalibrated the PSOM for 31 10.50 15 tires using the code 9.14. Since doing that, the speedometer reads nearly 5 mph higher than it should at 70 mph. I'm wondering if I should reprogram it for a 30 9.50 15 tire using code 9.52 or try something in between those two. I have recalibrated the PSOM for this tire size before with the same setup on my last truck and the speedometer was accurate within 1-2 mph at 70.

 

I would suggest actually measuring the tire before recalibrating. Actual tire sizes vary between manufacturers even within the same "measurements"

 

I always use percentage to tell me how much. You need to reduce speed by 7%. How much was it off before you did the calibration?

 

It seemed to read about 5 mph low, but I never checked it with GPS before recalibrating it.

 

I've forgotten now, it's been so long, but aren't you only allowed a certain number of times you can reset the tire rotation value?

 

I believe that number is 6

 

Yeah, it is limited to 6 so there are 5 remaining. I have no idea why Ford designed it that way.

 

I think the older PSOM's are only allowed 3 changes. Mine is a 92, and does NOT show how many calibration changes remaining, which I have read means it was limited to 3.

 

To keep odometer fraud from occurring is main reason.

There is a way to reset that back to 6 just need to be able to copy and write the EEPROM of the PSOM.......and no anything over 6 will crash it....