Circuit Description
WARNING: This page is about a different car, the 2007 Pontiac Montana SV6, 2007 Chevrolet Uplander, and 2007 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
There are 2 different communication networks available on this vehicle: The class 2 network and the GMLAN network. The class 2 serial data circuit is the low speed link, and the GMLAN serial data circuit is the high speed link. Modules that need real time communications are attached to the high speed network. The (LZ9) engine control module (ECM) is the gateway between the networks. The purpose of the gateway is to transfer information from one network to another. If the vehicle is equipped with an (LX9) power train then the vehicle does not utilize the GMLAN high speed circuit; only the class 2 serial data circuit is installed.