Quote Originally Posted by kur4o View Post
On y-body there is no idle traffic. The ccm is the master bus.
That`s why there is problem with oem tool to communicate with y-body calibrations. It is waiting for idle traffic from ccm and sends f1 56 00[enter normal state message], since I don`t have corvette ccm connected on the main bus the tool refuse to communicate. It is possible that y-body still connect via aldl line since I hooked elm device to sniff traffic and there is no data send over class 2 data[maybe it is waiting for ccm data first or it is not using common obd2 protocol.
that's my observation too. the corvette doesn't have much crazy traffic on that line, but i've found people that connect before starting the vehicle have a bit better luck. i doubt they would have bothered to push all the obd-ii pids on the obd-i datastream. i bet 'class 2 serial data' is mostly unused.

I checked buick bin and there is much more idle traffic sent from pcm. ALDL message located at this address.
F2 CB
F2 D7
F2 F5
F3 1B
F3 25
F3 2F
F3 39
There is really long messages out there.
you have no idea. there's barely a gap, but there are gaps. i think if i just saturate the bus to shut up the CCM first so the heartbeat goes away then maybe any other modules that are problematic, i'll be OK.

how i do it already for f-bodies, but they have an approx 30msec gap between idle traffic, so if i use a 75ms gap between my messages, it pretty much always lands on a blank spot within a few tries.

i had a very helpful user (who is testing this stuff for me) dump a buick and a caddy, both key on and key off. file attached.

there's a ton of junk on that bus. look at this, maybe you can make sense of it, i sure can't! he can make it connect by pulling fuses, but he says there are three fuses, so i think the CCM heartbeat isn't enough (maybe another device takes over as master?)