CAN Databus, BEAN, UART, AVC-LAN,Vehicle networks, Multiplex wiring, Vehicle multiplex systems, Car network, Car networks, Vehicle data circuits, Vehicle data diagnistics


Workshop Activities	Multiplex Network Systems We are now beginning to see the problems created due to the ignorance of multiplex wiring systems or vehicle networks. Gone are the days when you can chop out or add in bits of electrical circuit. YES it may have a wire going to it. NO it does not go to the switch you may expect. Vehicles built from 2000 will start to incorporate multiplex wiring systems. What is a multiplex wiring system? The vehicle normally has a pair of communication cables running around the body, stopping off at termination boxes. This is similar to a street of houses having telephone lines connected to each house. Each termination is capable of handling a huge amount of data, ask your pc.	Technical Topics















	For example when you move a light switch the light comes on. The light switch will send a message down the data cable to a switch station. The switch station is typically a body controller module behind the dash board. This controller will consider the request, to operate a light, then output the corresponding signal to a relay operating the light. This simple example is duplicated for all the vehicles electric, that is everything in the car, everything under the bonnet, transmission, braking, traction control air conditioning the list goes on…... The body controller is continually monitoring everything. Should you try to swap, modify, remove, anything with a wire to it, the body controller will find out and at best log a fault code. If you really upset the controller it will throw a mega strop and your car will not start. You will be off to an expert centre in your area to correct the fault. History Over the past 20 years vehicle electronics and associated diagnostics have evolved. The 1980’s saw the start of electronic communication and the ability of a vehicle computer to produce fault codes in an effort to assist diagnostics. During the 1990’s serial data became common and diagnostic kit was made available to read data such as injection duration and ignition timing. Later came the ability to monitor systems, correct them and advise of the computers correction factors, such as fuelling requirements. The next step, in an effort to stop vehicle theft, was to start coding items. Before systems will operate happily they require a hand shake with the vehicles electronic code. Radios will not work if they can not shake the hand of the master computer or Body Control computer when switched on. The ignition key needs a hand shake before the vehicle will start. Many vehicle components have the same requirement. ¤ Basic diagnostic kit can read fault codes. ¤ Most kit can read running date ¤ Better quality kit can interrogate vehicle correction factors for things like fuelling adjustments. ¤ Quality kit may be able to put out service lights and have a conversation with the Body Controller. ¤ Dealer level diagnostic kit can do everything including security checks, code keys and programme all other electrical components to the Body Controller. Some independent garages have the top level kit and can offer you a main dealer service for diagnostics. If you want to know about vehicle networks try: Information from Bosch http://researchinfo.bosch.com/content/language2/html/5585.htm AVC-LAN system Audio Visual Communication http://perens.com/works/hobbies/ham/prius/avc-lan/avc-lan.pdf Testing the CAN Databus http://www.picoauto.com/automotivetopics/canbus.html BEAN Body Electronic Area Network http://www.motor.org.uk/documentlibrary/Tech%20Talk/Tech%20Tals%20-%20September%2005.pdf and more: http://en.wikipedia.org/wiki/Vehicle_bus http://www.can-cia.org/index.php?id=228 A partnership established 1983 Telephone 01443 231135 Pratt's Garage, Unit 5 Cambrian Ind. Est. Coed Cae Lane, Pontyclun, CF72 9EW The web site sets out typical work undertaken and some technical topics which may interest you.