Hi all,

I recently finished up our Holley EFI to N2k gateways for the performance boat guys. Now starting work on a firmware to do HS GMLAN to J1939 and N2k protocol gauge output. Since I don't have a LS vehicle handy, I borrowed a customers 08 Duramax to capture some high speed data packets. Jacked into the engine harness bus where it enters the body control module, and then after starting, unplugged the BCM to isolate the ECM/TCM data.

As many of you may know the BCM acts as the gateway between ECM and IP cluster which runs over the low speed LAN. I was guessing that GM streamed the gauge info out of the ECM all the time. Then the BCM would translate to the low speed protocol used by the gauge cluster. My testing so far doesn't back up this theory... Look like the BCM requests the data several times per second.

While capturing raw engine packets I also Tee'd in a couple scanners, Torque and EFIlive. I was able to request all the normal gauge PID's like oil press, temps, MAP, TPS and such using OBD-II without the BCM in play. However OBD request always have some lag to them. So my question is, has anyone taken the time to reverse engineer much of the high speed GMLAN packets?

Before I dive into this, figured would be worth asking what others have accomplished on it. If we have to use OBD-II pids to request the data, then we will. But I guessing there's a smoother way this could be accomplished. The goal is to get stuff like boost and tach data into our gateway at 10hz or quicker, then process into a industry standard output with least delay.