Ks150

I am having a similar problem with calibrating the speedometer on a 2011 F150. I have not changed the tire size or anything but I did take a PCM out of another Salvage truck and put it in my truck. The Salvage truck it came out of had 3.73 gears and the truck I have has 3.31 gears. The speedometer is off by 10%. I have been to the dealer twice and changed the axle ratio to match the 3.31 and nothing changed. We took the computer with on the drive and stopped and changed axle ratio to 3.15 and tire size and again nothing changed. The dealer tech said he was doing all he could and wasn't sure why it wasn't changing. Is there something he is missing?

RLH6805 I noticed that in the attachment that beside the axle ratio and tire size it says you are programming the PCM. However when my dealer tech was programming the axle ratio he was changing it in the BCM (Body Control Module). Is this by chance where were running into a problem? He said the speedometer reading has nothing to do with the PCM, However I'm not sure that is correct. Because the only thing I changed to make a difference on the speedometer is the PCM.

Dealer is stumped but I'm sure it can be changed. Its not like I'm doing something the truck is not supposed to do. Everything is stock just trying to tell the PCM this truck has 3.31 gears and not 3.73 gears like the other Salvage truck.

rlh6805

Hello,

I am confused as to what the dealer tech is doing then. In order to change the tire size or axle ratio parameters you need to go into PCM module programming. That option isn't even available for the BCM (at least not for our F150's).

montanaman

[QUOTE=rlh6805;1705540]Here is a screen shot from IDS showing the available tire sizes. The numbers next to the sizes are the Rev's Per Mile numbers.


That's useful info - thanks.

Ks150

He was going through Programable parameters to BCM and then the axle ratio and tire size was two of the options that you could change on the BCM. When he went to programable parameters for the PCM there wasn't anything about ratio or tire size there. Cruise control was about the only parameter in the PCM section.

rlh6805

I just noticed that you have a 2011. It is possible that Ford made a change as to which module that info is stored in. I have a 2010 myself and that for sure is the PCM. Are both the module and the truck 2011? Also, it is very important that the module part numbers are comparable. There are several HW variations for each module.

Ks150

That could be a possibilty that they changed that with the model year. The module and truck are both 2011 and all the nubmers were correct from the old module to the new module. When I read in the shop manual it does state that the PCM recieves vehicle speed information from the sensors and then relays it to the BCM and the BCM acts as the Gateway module and tells everything else what the speed is. It says that the PCM has a VIN block that stores the VIN #, axle ratio and also tire size. The tech never did anything with a VIN block of any kind to my knowledge. This could maybe have something to do that when I hook up my DTC scan tool (non-ford) it still gives the old VIN for the PCM. The tech said that was alright that it still shows the old VIN because it will always keep that in there. I would think that if the old VIN is still in there the old axle ratio is most likely too.

rlh6805

Ok, Now I have a better understanding as to what you are trying to do. Question; do you have the original module for that truck? If so, then the proper way to replace it would be to do a "Programmable Module Replacement" through IDS. What it does is sucks the info from the old module (VID block and cal) and installs it into the new one. If you don't have the old module then the tech is correct that the VIN cannot be changed. However, I still believe that the tire size info should be able to be changed. Where are you located? If you happen to be in SE MI I could help you.

Ks150

I do have the old module however it was smashed up pretty good where the plugs are. Do you have to have it plugged into the truck to take the info from it? Will the axle ratio and tire size be in programable parameters or where will it most likely be found? I am located in central Kansas. Thanks so much for the information its very helpful electronics on these trucks are crazy.

rlh6805

The old module needs to be able to be powered up. It isn't necessary to install it in the truck if someone has the proper set up (16 pin break out box and power supply) to power it up and connect IDS to pull out the info from it. It does sound like, however, that if the old module is smashed up that it probably has damage to it's internal circuit boards and therefor the original info is lost. I still cannot believe that you cannot program the proper tire size and axle ratio into the new module. I will have to look at this further when I get back to work on Monday. I probably can come up with a 2011 module and poke around using IDS to see what is available. If I don't get back to you by later next week, go ahead and post on here again and I will receive an email notification and that will be my reminder.

FX4 BUD

I'm about to pull the trigger on 35" ATZs but after reading this it sounds like I'm going to have a problem with my speedo and shift points?
I like to tow with my truck so this could be bad all over.
I'm going to go to my local dealer today to look into this