Cheksum of a SAAB IPC
Posted: Fri Dec 16, 2022 2:24 am
Hi,
Anyone can do chk for this ? search area en method of CHK
Anyone can do chk for this ? search area en method of CHK
Finally i get the CHK right! This probally just a part of file since it comes from TIS to web but that have dosen`t mather;-)
After i have cheked around all GM files actually have chk 0000 calculated over all data so normally you calculate chk by do big endian 16bit or litele endian 16 bit exept 2 first byte. Then you second complient on result and put in 2 first byte. How ever the checksum over all byte including 2 first is allways 0x0000. So in my case i only put 2 extra byte in my file compensate it so CHK over complete file is 0x0000 do my change and calculate chk over evrything exept 2 first byte do second compliente put the result in 2 first byte. chek so i have chk 0x0000 over complete file if it`s ok i remove my added byte;-) doubele check so i get same CHK over complete file that i hade in my file from tis to web and you have good chk.
Hope this help some other with CHK problems in GM ECU:s. I add file with my 2 compensate byte added.