Description

DESCRIPTION

The primary on-board communication network between microprocessor-based electronic control modules in this vehicle is the Controller Area Network (CAN) data bus system. However, on models with an optional 1.6 liter engine the Powertrain Control Module (PCM) uses the DaimlerChrysler Programmable Communication Interface (PCI) data bus system in combination with the CAN bus to form a hybrid 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.

The CAN bus is a two-wire multiplex system, while the PCI bus is a single-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 all vehicle nodes, except on vehicles with the 1.6 liter engine where the PCM uses the PCI bus. In addition, certain vehicles may also be equipped with a Serial Controller Interface (SCI) or a K-Line serial link bus to provide direct diagnostic access between a diagnostic scan tool connected to the industry-standard 16-way Data Link Connector (DLC) located below the driver side instrument panel and certain powertrain nodes.

There are actually three separate CAN bus systems used in the vehicle. They are designated: the CAN-B, the CAN-C and the Diagnostic CAN-C. The CAN-B and CAN-C systems provide on-board communication between all nodes in the vehicle. The CAN-C is the faster of the two systems providing near real-time communication (500 Kbps), but is less fault tolerant than the CAN-B system. The CAN-C is used exclusively for communications between critical powertrain and chassis nodes. The slower (83.3 Kbps), but more fault tolerant CAN-B system is used for communications between body and interior nodes. The CAN-B fault tolerance comes from its ability to revert to a single wire communication mode if there is a fault in the bus wiring.

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 Diagnostic CAN-C bus is also capable of 500 Kbps communication, and is sometimes informally referred to as the CAN-D system to differentiate it from the other high speed CAN-C bus. The Diagnostic CAN-C is used exclusively for the transmission of diagnostic information between the Totally Integrated Power Module/Central GateWay (TIPM or TIPMCGW) and a diagnostic scan tool connected to the DLC.

All models have a central CAN gateway or hub module integral to the TIPM that is connected to all three CAN buses. The TIPM is located in the engine compartment near the battery. This gateway physically and electrically isolates the CAN buses from each other and coordinates the bi-directional transfer of messages between them. On models with the 1.6 liter engine a separate, dedicated gateway module secured to the floor under the driver side front seat in the passenger compartment coordinates the bi-directional transfer of messages between the PCI bus line from the PCM and the CAN bus connected to all of the other nodes in the vehicle. There are no domestic market applications using the 1.6 liter engine.