6A1/6A2

Posted by mcaldwelva on Nov 18, 2015; 5:03pm
URL: http://bluesaab-forum.90.s1.nabble.com/6A1-6A2-tp15.html

Has anyone been able to decipher what these messages mean? I noticed issues with my SID calculating mpg and this seems to be the source. What I noticed is that the mpg wasn't changing. I started clearing the SID every couple days and check the mpg periodically and find that it was always stuck at 00.0 or 99.9. I tried various changes to my 6a2 message and it seemed to have a direct affect on this behavior.

From the ecu project, these seem to be typical message sequences:

power-up
6A1 21 00 00 13 01 02 44 00
6A2 32 00 00 03 01 02 00 00
6A2 42 00 00 22 00 00 00 00
6A2 52 00 00 22 00 00 00 00
6A2 62 00 00 22 00 00 00 00

active (repeated every 2 seconds)
6A1 21 00 00 12 01 02 44 00
6A2 32 00 00 16 01 02 00 00
6A2 42 00 00 36 00 00 00 00
6A2 52 00 00 36 00 00 00 00
6A2 62 00 00 36 00 00 00 00

power-down 
6A1 21 00 00 18 01 00 00 00
6A2 32 00 00 18 01 00 00 00
6A2 42 00 00 38 00 00 00 00
6A2 52 00 00 38 00 00 00 00
6A2 62 00 00 38 00 00 00 00

The only thing I've been able to see from sniffing 6a1 is that data[3] isn't always 13, 12, 18.  I do always see {2,3,8} on the bottom half but I've seen {0,1,2,3} in the top half at various times. So I think just the bottom half is the power-on/active/power-off part of the message.

Based on that, I'm sending the first corresponding 6a2 message from above. Now with that change, when I reset my computer, it appears to calculate mpg correctly for a while, but it eventually gets stuck at other some other absurd number. Has anyone else seen any issues like this?