can some one explain checksums for me?

[H1GHROLLR]

HEY PEOPLE , very very new to all this and im getting a bit worried about all this talk of CHECKSUMS , what is it ?? ,what does it do ???,how do i know if the .xdf im using has it on, and also what can i do to

remove/bypass it in tunerpro .. . . . . .cheers again guys

[VL400]

What else do you want to know??

A checksum is used to verify the memcal code is correct (see here for an explanation http://en.wikipedia.org/wiki/Checksum). When you change the tune you will make the checksum different. If you dont change the stored checksum when the ECU code boots up it will think something is wrong and will be in limp home mode. You can either let tunerpro handle the checksum calc (if setup it does this whenever you save the bin) or bypass the checksum. To bypass it make the device ID AA instead of 12 for the VR. The device ID is defined in the XDF and called 'Program ID Word'. It also mentions the AA to bypass checksum.

The checksum is under the XDF settings. Click the XDF drop down menu, then XDF header editor. There is a tab called checksums. You can then adjust it to suit. The $12 XDF i pointed you to has it set so you dont need to worry about it, the checksum will be updated when saving the bin.

[H1GHROLLR]

i dont understand this part

To bypass it make the device ID AA instead of 12 for the VR. The device ID is defined in the XDF and called 'Program ID Word'. It also mentions the AA to bypass checksum.

or this part

There is a tab called checksums. You can then adjust it to suit

[VL400]

To bypass it make the device ID AA instead of 12 for the VR. The device ID is defined in the XDF and called 'Program ID Word'. It also mentions the AA to bypass checksum.

Open tunerpro, open the XDF and bin to suit. Find program ID under the constants. Depending on what XDF/Bin your using it will be whatever the code base is. For the VR auto you were using earlier it will say '11'. Change this to AA and the checksum wont be used.

There is a tab called checksums. You can then adjust it to suit

Open tunerpro, open the XDF and bin your using. Click the 'XDF' drop down menu next to the 'file' menu, then XDF header editor. There is a tab called checksums. You can then adjust it to suit the code base. The $12 XDF i pointed you to has it set so you dont need to worry about it, the checksum will be updated when saving the bin. The $11 code must use AA in the device ID as tunerpro cant handle the way GM did the checksum.

[H1GHROLLR]

ok for example here is a screen shot of a VN tune im doing i clicked on all the stuff you said , now where is the section that i modify to AA etc . . .

DSC00969.jpg (155.85 KiB) Viewed 7764 times

[yoda69]

In the scalras there should be something like "Program ID" or similar. For $5D file it is set to $5D (work in hex), for $11 it is $11 etc.
In the $5D it is called "KKKPGMID: Program ID word - $5D=1989 $AA=bypass sumcheck"

Change this value to $AA to bypass checksum, this works on all known holden memcal based ECU's.

yoda69

[H1GHROLLR]

cool , what is SCALRAS

[VL400]

typo. In tunerpro it says Constants/Scalars and in there you will find the program ID.

[H1GHROLLR]

sorry guys i have only been working with tuning for 1 day , im a dumb s**t at it

[yoda69]

Scalars, my typo.
On the XDF Item Tree, there are Scalars, Flags and Tables.
Scalars are typically and 8 or16 bit (1 or 2 byte) address to store information, ie RPM limit.
Flags are for changinging individual bits within a byte. Used for things like VATS, Lean Cruise, Manual/Auto, etc.
Tables are for 2D or 3D info, eg Idle RPM (2D), Spark Table (3D), etc.

Have a look at the Tunerpro help files for more detailed information or do a google search, there is lots of info already out there.

yoda69