How is a checksum calculated? I cannot see enough information in the specs to fully calculate it. How does it change for each of the protocols?
I have been using the OBDsim with great success when evaluating different OBD software packages. But when I came across the TouchScan program I realized that the OBDsim didn't output the checksum when the headers was enabled (ATH1 command; the ELM327 do in fact output the check sum), as I was missing this byte the TouchScan program reported an error and was unable to connect to the OBDsim.