Yesterday I went to flash an 09 6.7 So to start with I downloaded the stock tune with no problems, tune said "OK TO FLASH" but since I have never been able to get the see dealer timer part of the tunes to show up for me with not being able to extract the Zip file that was provided on the forum months ago i used a known clean file that I had another member change the timer for me. changed the VIN and went to flash it in and it got a 1/3 of the way and gave me the $0548 message and stopped flashing. so i disabled the Checksum in the tune and it flashed in fine but when I started it I had the p0601 fault code for invalid checksum. I then used another tune I have used many times before and flashed in with the checksum enabled and had no further issues.
So what exactly is the "checksum"? and what does it do? any idea why I got the $0548 error message?