Reading a tune and modifying it. so many questions ;-)

hey all!
so I'm fairly new to tuning, bu tI have an EE background... not sure if that will help much other than I know how to burn a chip LOL

speaking for my 1987 Vette here: So I have a tune that was given to me, they are reputable so I'm not concerned in that manner, but I want to read it and see what settings are put in for like the fan and what not.
I know it's a 16k read, so I set Moates flash &burn to 00c0000-00efff and read the data. I opened it in tunerpro, and applied the $32B XDF and I "think" I'm reading it properly.


I guess my question is how can I be sure I have the correct XDF file?
what would happen if I made a change, burned it on a spare chip, and I used the wrong XDF without knowing it?

someone told me once that it's possible to "lock" a tune by the professional tuners, how can I tell fi this one is locked?
If it's locked I'll basically just give up trying to change this one.

thanks all!
Mike B

If you use the wrong XDF, you usually get garbled maps, and/or values that make little to no sense.

If you modify a bin with the wrong XDF, you will likely be changing things that aren't what you think they are. You may not notice anything wrong, or you may get a corrupted bin that will cause a code 51 if inserted into the ECM.

Some maps and variables are in common locations and will show fine with the wrong XDF, especially closely related masks, that are used in the same ECM, but other things will have moved locations and/or have added/removed variables... so... Knowing you are using the right XDF is a little bit experience, and a little bit fining good resources for knowing what cars/engines use what XDF. There is also a byte in the BIN that will show you the mask, in most BINs (there are exceptions, like anything that is longer than 2 digits), but this byte can be in different places in different masks/BINs. Most are located at 0x08.

It's not possible to "lock" OBD1 GM BINs, however, some companies have gone as far as shifting the entire bin by a byte or two, and updating pointers to work correctly, or moving instructions and variables around to make it more difficult to know what has been changed in the BIN.

you can do a compare with the stock version of the same calibration if you can find it. the bin compare tool will show you what's changed. if its been monkeyed with, unless they have a more complete definition than you, there will be differences in undefined regions rather than tables

thank you both for the replies!

glad to know an obd1 cannot be locked, so I guess my only question would be is there a "newer" $32B XDF? I'll try to source a stock chip, I can always pull mine out of my vette and read that one as well. but would be nice to try and find the BIN itself.

The newest $32B is the one right here on GearHead EFI, posted by EagleMark in that ECM's thread. If that's the one you have, you're golden. :thumbsup: