Hybrid Bus

WARNING: This page is about a different car, the 2007 Chrysler PT Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

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 vehicles equipped 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 system, which forms 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 for communication. 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 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 of the nodes that are connected to them. The CAN-C is the faster of the systems, providing near real-time communication (500 Kbps), but is less fault tolerant than the CAN-B system. The CAN-C is used typically for communications between more critical nodes, while the slower (83.3 Kbps), but more fault tolerant CAN-B system is used for communications between less critical 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. Slower still, the PCI bus communicates at 10.4 Kbps.

The added speed of the CAN data bus network or the CAN and PCI hybrid data bus network 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 (TIPM) and a diagnostic scan tool connected to the DLC. The DLC also has circuits connected directly to the PCI and SCI bus circuits of vehicles that are so equipped.

All vehicles have a CAN Central GateWay (CGW or TIPMCGW) or hub module integral to the TIPM that is connected to all three CAN buses. This gateway physically and electrically isolates the CAN buses from each other and coordinates the bi-directional transfer of messages between them. Vehicles equipped with the 1.6 liter engine also have a separate dedicated gateway module secured to the floor under the driver side front seat in the passenger compartment. This separate gateway module isolates the PCI bus from the CAN bus and coordinates the bi-directional transfer of messages between the PCM PCI bus and the CAN bus connected to all other nodes in the vehicle. There are no domestic market applications using the 1.6 liter engine.