Does not every file have a checksum?
Because when I take C113, do NOT and +1, I am not arriving at CE35.

 

This is one of the 3 bin files from an Express van IPC calibration.

I see it has some clear text, I just wanted to play around and see if it's possible to change a word, for example change "TACHOMETER" to lowercase, or to "    RPM    ", without bricking the module. I have bricked 3 clusters so far (they are stuck in infinite loop), what am I doing wrong?

 

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Here is the 20908584.bin: https://www.dropbox.com/scl/fi/plozp4twu8575zny3jruf/20908584.bin?rlkey=iuvrgyzqqmfu9a1ucj3cqgyh2&dl=0

It's an IPC file for a 2012 Chevrolet Express.
Does anyone know what the checksum algorithm is on it? Neither Little- or Big-Endian make sense! 

I think I am onto something!!!

Here are 6 IPC files, from 3 vans: 2008, 2012 and 2018, and all have "Whole document Little-Endian" checksum ending in a5c3!

 

A little more digging. Each of those files actually ends in c3a5.

Okay, so here is the IPC checksum algorithm for the 2008-current GMT-610 Express vans:

Use Hex Editor Neo. Select the entire document !!except the last 2 bytes!!. The sum of Little-Endian 16-bit values must end in 0000. If you edit the file, modify the first 2 bytes accordingly, to arrive at 0000.