Section 11 (Electronic Control Modules (Service Information)): Communication: Description

POWERNET bus architecture 

The primary on-board communication network between microcontroller-based electronic control modules in this vehicle is the Controller Area Network (CAN) data bus system. A data bus network minimizes redundant wiring connections; and, at the same time, reduces wire harness complexity, sensor current loads and controller hardware by allowing each sensing device to be connected to only one module (also referred to as a node). Each node reads, then broadcasts its sensor data over the bus for use by all other nodes requiring that data. Each node ignores the messages on the bus that it cannot use. These networks are protected by a Security Gateway Module (SGW).

The CAN bus is a two-wire multiplex system. Multiplexing is any system that enables the transmission of multiple messages over a single channel or circuit. The CAN bus is used for communication between most vehicle nodes. However, in addition to the CAN bus network, certain nodes may also be equipped with a Local Interface Network (LIN) data bus. The LIN data bus is a single wire low-speed (9.6 Kbps) serial link bus used to provide direct communication between a LIN master module and certain switch or sensor inputs.

There are actually two separate CAN bus systems used in the vehicle. They are designated: the CAN-Chassis (CAN-C) and CAN-Interior High Speed (CAN-IHS). The CAN-C and CAN-IHS systems provide on-board communication between all of the nodes that are connected to them. The CAN-C is the faster of the two systems providing near real-time communication (500 Kbps). The CAN-C is used typically for communications between more critical nodes, while the slower (125 Kbps). The CAN-IHS system is used for communications between less critical nodes. This electronics architecture is called Powernet.

The added speed of the CAN data bus is many times faster than previous data bus systems. This added speed facilitates the addition of more electronic control modules or nodes and the incorporation of many new electrical and electronic features in the vehicle.

The Body Control Module (BCM) is located under the instrument panel to right of the glove box. The central CAN gateway or hub module integral to the BCM is connected to CAN-C and CAN-IHS buses. This gateway physically and electrically isolates the CAN buses from each other and coordinates the bi-directional transfer of messages between them.

All modules transmit and receive messages over one of these buses. Data exchange between the modules is achieved by serial transmission of encoded data messages (a form of transmission in which data bits are sent sequentially, one at a time, over a single line). Each module can both send and receive serial data simultaneously. Each data bit of a CAN Bus message is carried over the bus as a voltage differential between the two bus circuits which, when strung together, form a message. Each module uses arbitration to sort the message priority if two competing messages are attempting to be broadcast at the same time. Corruption of a single bit within a message will corrupt the entire message. Each message contains a Cyclic Redundancy Check (CRC) which specifies the message size exactly. If the message detected conflicts with the CRC the Electronic Control Unit (ECU) receiving it will determine the message to be an error and consider that communication has not been possible. Diagnosis of this condition using a lab scope may reveal activity that appears to be bus data messages even if no actual communication is possible. Communication problems that affect the whole bus, as a result of opens and terminal push outs are more likely to occur on data busses that operate at a high speed than a data bus that operates at a lower speed

CAN DOMINANT NODES 

CAN-C is the main 500k network and is terminated by the two star connectors.

• For a complete CAN C BUS LAYOUT wiring diagram, refer to the appropriate Wiring Information  .
• For a complete CAN C BUS SYSTEM wiring diagram, refer to the appropriate Wiring Information  .

CAN-IHS is the main 125k network and is terminated by the two star connectors.

• For a complete CAN IHS BUS LAYOUT wiring diagram, refer to the appropriate Wiring Information 
• For a complete CAN IHS BUS SYSTEM wiring diagram, refer to the appropriate Wiring Information 

CAN-C1 is a private network between the Adaptive Cruise Control (ACC) Module and the Forward Facing Camera (FFC) module and is terminated by both modules.

CAN-C2 is a private network between the Transmission Control Module (TCM) and the Electronic Shift Module (ESM) and is terminated by both modules.

CAN-IHS 2 is terminated by the SGW and the radio.

CAN-C6 is the diagnostic network and is terminated by the SGW.

CAN-C8 is the network for unprotected ECUs and is terminated by the SGW and the radio.

LIN 

In addition to the CAN bus network, certain ECUs may also be equipped with a Local Interface Network (LIN) data bus. The LIN data bus is a single wire low-speed (9.6 Kbps) serial link bus used to provide direct communication between a LIN master module and certain switch or sensor inputs based on vehicle configuration. There is also a private security bus network between the Radio Frequency Hub (RFH) Module and the Keyless Ignition Node (KIN) known as the Security K Line Communication Bus.

For a complete LIN BUS SYSTEM wiring diagram, refer to the appropriate Wiring Information  .