Information Bus: Description and Operation

Data Link Communications Description and Operation

Circuit Description
The vehicle is fitted with a new powertrain interface module (PIM). The most significant changes that have been made to the PIM are as follows:
- Communication protocol between the engine control module (ECM), transmission control module (TCM) and the Electronic Control Unit (ECU) of the Antilock Braking and Traction Control System, is General Motors Local Area Network (GM LAN) .
- ECM to PIM authentication for vehicle security.
- Cruise control switch functions input directly into the PIM.

The various electronic control modules integrated into the vehicle communicate with each other through the serial data bus. The ECM, TCM and ECU of the ABS communicate on the serial data bus using the GM LAN communication protocol, while the PIM communicates with the instrument cluster.

The PIM is integrated into the serial data network and acts as a transparent bi-directional translation device that enables the control modules on the GM LAN serial data bus to communicate with control modules on the UART serial data bus.