I've had my Ex for about 3 months now. After reading a bunch of posts here I've decided that I might want to do a PCM reset so that the Ex can learn my driving habits. I do have a question though. Someone in one thread mentioned that after a PCM reset the tire size would have to be reset if I have anything but stock size tires. I have oversized 33.5" tires. I already had the dealer reset the tire size when they were doing some warranty work for me. If I reset the PCM will that be erased or will that tire size still be in the computer? Also, there are a lot of different methods that people suggest to do the PCM reset. I thought I read somewhere the actual Ford specified (?) way of doing it, but can't find it now. Any help would be appreciated. Thanks.
Your PCM is a computer, the part that stores programming is the hard drive. Hard drives store non-volitile data, meaning that when you unplug the computer or shut it down, the data is still there no matter what.
In another part of the PCM, lies the shift strategy and DTC storage. (i.e RAM or Memory chips in a computer) Where it lies is the volitile part of the PCM. When PCM looses power completely, that's the only part that gets wiped.
So no need to worry, disconnect your batteries, turn the lights on, wait 30 mins or so, connect the batteries and go.
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I've decided that I might want to do a PCM reset so that the Ex can learn my driving habits.
It doesn't learn driving habits.
The engine will learn a fuel adjustment to get the optimal fuel/air ratio. The trans will learn some pressure adjustments to make each shift have the proper slip time. There's nothing in the software that learns anything about driving habits.
Having said that it won't hurt anything to do a reset. Just don't expect it to drive better after the reset. In fact, until it relearns everything it lost in the reset expect it to drive worse for a while.
__________________ Mark Former Ford Automatic Transmission Engineer 1988 - 2007
“The good thing about science is that it's true whether or not you believe in it.” ― Neil deGrasse Tyson
No need to disconnect the battery... If you do, you'll also have to reset your clok and your presets.
There is a single fuse in Fords that, when pulled, removes Keep-Alive power to the NVRAM. Pull that fuse, go take a break for 10-15 minutes, reinstall it, and your PCM will be reset back to the baseline programming.
On the 03 Excursion, it appears that F2.36 is the one.
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