b'an AutomotiveTechInfo.com publicationThe ConundrumUntangling CAN and other communication bus line issues in Porsche car lines presents technicians with a unique challenge. Over the last 30 years or so, automotive communications networks have morphed from their humble origins. In the beginning, these networks were only single-purpose, hard-wired, dedicated slave modules intended to communicate with and control singular engine control functions. They have evolved to where we sit today, working on the newest of platforms, where Porsches coming into our bays now have more than ten interconnected networks and multiple network protocols running in one vehicle platform.CAN, LIN, SENT, FlexRay, Ethernet, MOST, and many other different communication protocols can be found in Porsche vehicles, depending on the year, model, and era of the car in front of you. The challenge for us as technicians in the field, is that we only have the Physical Layer of the CAN bus to work with to track down network issues. The Physical Layer is where the automotive technician spendsFigure 1: Part of the Network Diagram for a 2017 Macan, shows how many modules, 95+ percent of his or her time on diagnostic efforts; more on that in a minute. Application Data Link The rest of CANs operational scheme is largely untouchable by technicians, with the exception of software programming, of course. The issue for technicians with CAN and network diagnostics in general is that the Presentation LLC software, the data packet, coding database (translator database), and the way that the systems data channels are configured, are all 100% OEM proprietary information. Neither the configuration nor content Session MAC of the data are standardized throughout all car lines, but the Transport Layer is. The Transport Layer is the standardized format in which the data packet must be carried, as well as the physical network. This forms Transport Physical the CAN standard, but what is inside the data packet is all proprietary.PLSNetwork Many actuations of critical output functions and input sensor data are shared via CAN. A single module, PMA the ECM for example, processes a set of signals from hard wired sensors, but then a CAN message is Data Link PMS configured and broadcast to all other interested modules, which then act on that data. So, after testing the inputs, outputs, or wiring of any given control circuit, automotive technicians currently have no way to Physical MDI trace a message from, say a window switch (which is a CAN node itself), through the Gateway, to the BCM, and then to the Door Control Module (which is the module that actually runs the window motor). We currently have absolutely no easy way to do this, without becoming de-bugging specialists.7 8'