Does anybody have wiring diagrams that shows the gmlan circuit and where the pins are on the BCM? Pretty sure I've found where they are on the OBDII port and I have ECU/TCM diagrams. Any assistance with how to troubleshoot the system past checking resistance would be greatly appreciated as well.

Fwiw I'm not getting a cel on the dash but I do have abs fault and traction control off messages that come up immediately even after disconnecting the battery for a while. After letting the car run about 7 minutes I get contact dealer and the tach/speedo/temp/gas indicators ask drop to zero.

A maxysis scan tool was able to find several codes including a u0073 code that comes back immediately after deleting all codes.

Also this is a manual swap that has been running fantastic for about a month or more. And was running decent for a while prior to that.