How is it calculated… I’ve burned a whole series of chips tonight that do nothing but put the ecm in limphome mode (fast flashing CES light). The last time I had this issue it was using the latest and greatest $58 xdf which later on I got a reaponse “Oh, we new it calculated it wrong… sorry…”

So the question becomes, is there an alterative way of calculating or doublechecking a checksum?

 

It is an 8-bit checksum. If you only changed one or two values you can figure it out be subracting/adding to the checksum from what it was with the old values. Other way it to calculate it using a C program using byte as the types. In any case, not worth the effort.

Download the rr_v14.ecu file and use that. It is correct and has a lot of the info that is missing from other xdf/ecu files.

 

Isn't that a $58 style .ecu file? I'm messing with a '299/$99

 

Yes, it is $58. You posted only $58 info.

 

Basically what the checksum does is add up every value in the binary as a single byte. If it goes greater than 255 it wraps around to 0 again.

http://wasabi.dynu.com:8080/wiki/ind...68HC11Checksum

The bin editor programs all calculate the checksum for you.

 

Because that was the last time that I had that same problem, and I think it was v13 or the original reliese of v14, which is the reason that I’m asking.

So is there another way to calculate it? Or can I check to see if it is defined correctly in the .ecu or .xdf somehow (since they’re easy enough to edit if I knew how they were supposed to be calculating it)?

 

I found a checksum calculator if you are still interested. I tested it and it works properly. You have to zero out the first 8 bytes to get the proper GM checksum. This is because the calculator does the entire bin and GM only does the entire bin without the first 8 bytes. Let me know if you still need it.

 

As Alex pointed out, the editors calculate it for you. The problem with the ECU/XDF was that it had the incorrect bin size or incorrect checksum calculation. It has been corrected in the latest versions.

There is no need to calculate it externally. In fact, for tuning, I would highly recommend simply disabling it (by setting the mask ID byte to 0xAA).

 

Yes, the editors calculate it. I think he was looking for something to verify the editors calculation.

 

Right, exactly, I was looking for some simple/quick way to verify the checksum