[braines]

I looked and I hope this is the right way to be posting this:

I have a Sept. 1995 Volvo 850 turbo with 80,000 miles.
(Sept 1995 ->1996 model year => OBD II variant ISO 9141-2)

I tried to build my own with a proper ELM327, failed miserably probobly because I wasn't properly grounding/+5ving the pins for the unused protocals.
I came into a prebuilt circuit on Ebay for $25.

It still didn't work.

After futzing around I determined that the problem was in the 'ELM_INIT()' function and changing at '10F1' to a '6AF1' fixed the problem.

after the do while loop, after the 'ATDPN' command, the ATSH 6810F1 command for Protocol 3 (ISO 9141-2) was causing problems. After this command I would get 'NO DATA' from all subsequent commands.

First I tried 'ATSH 686AF1' instead of 'NO DATA' I started getting responses from 2 different computers in my old car which confused the OBDuino.

Eventually I found that 'ATSH 686AF0' was the magic phrase that worked.

I still don't really understand why this is the correct header or if this is the correct header for cars other than mine on the ISO 9141-2 variant, but I wanted to share the change I needed so that if other people are struggling with this that they investigate the headers.

I wonder if most of the development on the ELM portion of the code is related to the CAN protocol and if the ISO 9141-2 portion of the ELM init is largely untested? Have others had luck with the default 'Set Header' (ATSH) command in the code base?