Corvette CCM Reverse Engineering Anyone?

[NomakeWan]

i definitely seem to be getting some garbage but no heartbeat.

if i disconnect the CCM, the ecm responds, so i know it's alive.

i've tried both calibrations 16200891 and 16209281 from my site.

here's what the CCM is spitting out, the ECM does not seem to respond from what I can see, but the ECM is certainly there, as if i disconnect the CCM, the ECM responds.

any idea why they aren't handshaking or whatever they're s'posed to do ?

13430ms to 13540ms (110ms) :: 10590887020006 40574E9F7C 416702000087004800000000880004E84900A0A08A
::: GAP78ms
13618ms to 13743ms (125ms) :: 10590887020006 4057E84938 41670200008700480000000088000481DA00A0A060
::: GAP78ms
13821ms to 13946ms (125ms) :: 10590887020006 405781DA0E 4167020000870048000000008800041B8400A0A01C
::: GAP78ms
14024ms to 14149ms (125ms) :: 10590887020006 40571B84CA 416702000087004800000000880004B51500A0A0F1
::: GAP78ms
14227ms to 14352ms (125ms) :: 10590887020006 4057B5159F 4167020000870048000000008800044EC000A0A0AD
::: GAP78ms
14430ms to 14524ms (94ms) :: 10590887020006 40574EC05B 416702000087004800000000880004E85B00A0A078

That looks totally normal, and in fact the ECM response is right there. I'm not sure why EEHack's idle scan has such weird spacing, but it always has. I've altered your above logs to have the correct spacing to make it more clear.

To elaborate, the 10 message is the HVAC broadcast (no response expected), the 40 message is the CCM polling the ECM, and the 41 message is the ECM responding to the CCM.

What's interesting to note here are the timer bytes in the 41 response. This makes me really really really want to know what "word_1983" is in $EE, because whatever that timer is, it's apparently being used by the CCM. The values of those two bytes in the ECM's response then reappear in the mystery bytes of the CCM's next poll. This explains why the CCM's initial poll before the ECM comes online is 4057000069, and why eventually it just becomes 4057FFFF6B. But knowing what these intermediate values mean (and perhaps finding out why GM thought it important for the CCM to echo these values in the 40 poll, something they only started doing in 1992) would mean figuring out word_1983.

kur4o, any insight into that particular area of the $EE program?