GMLAN which stands for (General Motor Local Area Network) is an application- and transport-layer protocol using CAN for lower layer services. Transport-layer services include the transmission of multi-CAN-frame messages based on the ISO 15765-2 multi-frame messaging scheme. It was developed and is used primarily by General Motors for in-vehicle communication and diagnostics. GM's Tech2 uses the CANdi (Controller Area Network diagnostic interface) adapter to communicate over GMLAN.
Some software applications that allow interfacing to GMLAN are:
References
GMLAN Wikipedia(Text) CC BY-SA