Will changing values on spark advance tables cause a checksum erro in a GM OBD I PCM?

[sanderson231]

I acquired some modified bin files for a 4.9L Cadillac with a manual transmission. This engine only came with an auto from the factory). I got a checksum error when I looked at them with Tunercat. The documentation shows some changes to values in the spark advance tables. Is it to be expected that changing values in the spark advance tables would cause a checksum error?

[steveo]

changing anything would cause a checksum to be wrong, so saving the file in tuning software usually recalculates the checksum. so its possible the file you have is corrupt. thats what a checksum is for, to detect corruption. so now you would be at risk of the ecm crashing if you use that file

[sanderson231]

The weird thing is that I got 6 files. Four that were modified and two with the stock calibrations. The two with stock calibrations opened fine. The four that were modified had checksum errors when opening with Tunercat. The modified files are hand me downs that originated ~25 years ago. The check sum error flag (Error 51) was disabled. So maybe the way that these files were edited back then did not recalculate a new checksum

[steveo]

it's possible, in which case simple re-save the file with tunercat and the checksum will be corrected. at your own risk of course