GM TCM Checksum Calculation

American Delco GM ECUs and PCMs, ALDL, OBD 1.5.
ironduke
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Re: GM TCM Checksum Calculation

Post by ironduke »

There is a bunch of text in the middle of the file that does not look like calibration data to me, possible write up some code that does the 16 bit checksum and if it's wrong then it steps another byte and tries again.. It'd take a little while but doable.. What I don't know is if that's the whole cal file or if there is dead space defined somehow.
I am also used to seeing a checksum AND a CVN(usually a crc-16) but I don't see that in this file? why is that? Older OS doesn't have a CVN?? I'm used to looking at 08 and up to around 2013 but I only have had a glance at the T76 files..
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Re: GM TCM Checksum Calculation

Post by VX L67 Getrag »

Have you got the original un-edited version of the section you know the cks is correct for, that may help identify where it is & how to calculate it.
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Re: GM TCM Checksum Calculation

Post by Cuongcoco »

VX L67 Getrag wrote:Have you got the original un-edited version of the section you know the cks is correct for, that may help identify where it is & how to calculate it.
This is original file. I just try calculate checksum and haven’t edit data yet
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Re: GM TCM Checksum Calculation

Post by Cuongcoco »

ironduke wrote:There is a bunch of text in the middle of the file that does not look like calibration data to me, possible write up some code that does the 16 bit checksum and if it's wrong then it steps another byte and tries again.. It'd take a little while but doable.. What I don't know is if that's the whole cal file or if there is dead space defined somehow.
I am also used to seeing a checksum AND a CVN(usually a crc-16) but I don't see that in this file? why is that? Older OS doesn't have a CVN?? I'm used to looking at 08 and up to around 2013 but I only have had a glance at the T76 files..
Ah, you mean we can try take checksum 16 bit AND with CVN? I will try it, thank you
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Re: GM TCM Checksum Calculation

Post by VX L67 Getrag »

I don't think you're going to figure out the CKS of that entire file as it looks like there's comments added in which aren't part of a normal T76 calibration.
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Cuongcoco
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Re: GM TCM Checksum Calculation

Post by Cuongcoco »

ironduke wrote:There is a bunch of text in the middle of the file that does not look like calibration data to me, possible write up some code that does the 16 bit checksum and if it's wrong then it steps another byte and tries again.. It'd take a little while but doable.. What I don't know is if that's the whole cal file or if there is dead space defined somehow.
I am also used to seeing a checksum AND a CVN(usually a crc-16) but I don't see that in this file? why is that? Older OS doesn't have a CVN?? I'm used to looking at 08 and up to around 2013 but I only have had a glance at the T76 files..
This is a cvn I taked of this file
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Re: GM TCM Checksum Calculation

Post by antus »

I googled "AW 5AT C100 VM20S" which is in the file near the end, and landed on this: https://translate.google.com/translate? ... ch&pto=aue

There they say op-com is reporting for their captiva:

Box
ID: 0x0601 Hardware
number: 96625011
System name: AW 5AT C100 VM20S
Part number: 96625125 Software
version number: 05C26174
Programming Date: 20080129
Hardware key number: PCO1STN # 04
System description: AISIN0200

So I think that may be what you have, or very close to. It looks like an Aisin brand controller, so its probably a similar or same method of calculating sums as other aisin of the same era. I dont know how those work, but someone might?


Edit: A bit more playing around near that string and I am thinking like this:
Image18.png
Image18.png (170.81 KiB) Viewed 4523 times
I think there are a couple of sections in the file, and there is a small section at the end. So Im looking at that because its easier to highlight small chunks and see the whole segment. Ive highlighted what looks like the start of the section, as decimal its 96625143 (very similar to 96625125 above). So I think this might a small segment, closely related to but different from the one on the russian forums. Probably its the same controller, and you have an update to the above system. The green might be checksum for this segment, or the blue. The red is the system name. The yellow may or may not be part of it, same with the blue and the red. Ive tried all those combinations with sum16 crc16 and crc16-ccitt, but no match so far.
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
Cuongcoco
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Re: GM TCM Checksum Calculation

Post by Cuongcoco »

antus wrote:I googled "AW 5AT C100 VM20S" which is in the file near the end, and landed on this: https://translate.google.com/translate? ... ch&pto=aue

There they say op-com is reporting for their captiva:

Box
ID: 0x0601 Hardware
number: 96625011
System name: AW 5AT C100 VM20S
Part number: 96625125 Software
version number: 05C26174
Programming Date: 20080129
Hardware key number: PCO1STN # 04
System description: AISIN0200

So I think that may be what you have, or very close to. It looks like an Aisin brand controller, so its probably a similar or same method of calculating sums as other aisin of the same era. I dont know how those work, but someone might?
thank you, yes, this is my tcm information (very close to) as picture i show above.
Cuongcoco
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Re: GM TCM Checksum Calculation

Post by Cuongcoco »

ironduke wrote:There is a bunch of text in the middle of the file that does not look like calibration data to me, possible write up some code that does the 16 bit checksum and if it's wrong then it steps another byte and tries again.. It'd take a little while but doable.. What I don't know is if that's the whole cal file or if there is dead space defined somehow.
I am also used to seeing a checksum AND a CVN(usually a crc-16) but I don't see that in this file? why is that? Older OS doesn't have a CVN?? I'm used to looking at 08 and up to around 2013 but I only have had a glance at the T76 files..
hi
i checked again. CVN of this file is correct . checksum of whole file 96625143 is FD80(CRC-16). but it not haven't relationship with 2 first byte check sum of the file C7 F6
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Re: GM TCM Checksum Calculation

Post by antus »

The same ID is also here at the start of the file. Maybe were looking at a table of contents as well, at one or the other end.
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Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
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