Checksum vs CVN

Admittedly I'm new to all this, but I searched away and couldn't find a solution so I figured I'd post.

When I load Tune v7.5 and read an ECM I get the "Details" window on the right side of the screen. Under the "Calibration" tab it lists the Segment, ID, and Checksum. The only problem is the literature I have from GM shows a CVN and not a Checksum.

I thought these were different names for the same value, but apparently not! The checksum is a hex number that is very long (more digits) than the CVNs. So, now the question: how do I convert the Checksum values to CVN values?

Thanks!

For what purpose...?

A buddy has purchased a used truck and we are trying to see if the segments are stock GM ones or not. It's my understanding, correct me if I'm wrong, that if it was modified then we could tell. I have the stock GM CVN numbers, but it doesn't do much good if the software displays checksums instead of the CVNs.

V2 displays the CVN of each segment... i.e. on the V2 LCD... using the LCD menu look under Diagnostics.

I'm pretty sure there are some tuners out there that still don't change teh checksum when they modify a tune, so that isn't a guaranteed way to see if it was modified or not. I know a TECH 2 can tell you the last 10 flashes flashed into it if it is an LMM, and it can also scan the TCM to find the max torque input to tell if it was tuned or not.

Joe: will do, thanks.

Fermanator: great to know, thanks. I'm still wet behind the ears and I thought that the ecm calculates it automatically, but I guess that doesn't mean that it can't be over written. Now I understand some of the other posts I read! Thanks.


Now that's out of the way, I see one segment that says "Engine" and another that says "Engine Operation", what's the difference?