CAN digital wiring systems was first played about with by Bosch back in the 1980s.
I think Mercedes where the first car manufacturer to start using CAN digital systems in there cars, Then PSA Peugeot / Citroen followed on a few years later & now Ford, Vauxhall, VW, Fiat etc are going the same way.
Basically you have a thin twisted pair of wires in the cars main wiring loom, One is CAN - high & the other CAN - low.
The cars main body computer uses these to send digital signals to things like the radio, climate control, etc & to also talk to the engine ECU that's looking after the engine.
What should happen is the digital signal sent down one CAN wire should have an opposite mirror image on the other CAN wire.
What CAN was brought in for was to reduce weight & amount of wires running around the car.
If the CAN wires get interference from say an MOD radar station ( allegedly ) it can upset the digital system & can shut the cars electrical system down.
Electrical spikes & CAN wiring don't make a happy combination, Ask any TU petrol engine Peugeot / Citroen owner with a Sagem coil pack.
Also water getting into one of the connections for something on the CAN system can upset the electronics, Ask any multiplexed 406 saloon owner with a boot mounted cd changer after the rear light seal start leaking, Water then gets in to the cd changer, The cd changer is on the CAN system, The dash lights up like a xmas tree & the electric's go haywire.
Radio two drove a VW Passat past the radar station allegedly causing cars to shut down the other week, Nothing happened when they tried but they used an older Passat & NOT one equipped with a CAN digital wiring system so the test didnt help the more modern car owner at all.
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Arr, very interesting, thanks for the info.
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CAN digital wiring systems was first played about with by Bosch back in the 1980s.....
www.bba-reman.com/content.aspx?content=can_bus_con...y
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Any idea which car models /makes are worst affected. I would not be surprised if some makes use a nasty cheap version more vulnerable to interference than others.
madf
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No idea, Most CAN stuff is Bosch & that means it is top quality.
Its more down to the way it is installed in the car & how its looked after that lets it down & also who programmed the software.
Having alarms, car phones, tow bar electric's etc added on to a CAN equipped car by someone who isn't trained on CAN systems also causes great problems.
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I have read a lot about a place called Fylingdales in Yorkshire, it is an American defence system area, and causes severe havoc with cars, I'm sure their are plenty of websites about it. I have also read that there is a spy satellite network which monitors radio transmissions as small as a car locking remote, and this was one of the reasons all modern electrical appliances are CE approved and have loads of screening and metal internal encasments with finger gaskets etc... (to reduce RF pollution and keep the 'noise' down'.
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Another point to remember with a vehicle equipped with a CAN system is the battery.
If the battery goes flat be very careful using a jump box or jumpleads because the incorrect use of either of these can ruin the expensive control unit, You MUST follow the instructions in the owners handbook to the letter or seek the advice from a main dealer.
The best advice with CAN systems when jump-starting or for battery disconnection / reconnection is look in the owners manual.
It only takes a couple of minutes to read the owners manual but a less then a couple of seconds to do some very expensive damage to the vehicle.
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I thought the 1986 XJ40 was the first car to have CAN and mutiplex wiring?
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The XJ40 did have a lot of electrics & electronic control systems but it wasnt a CAN system.
Also most XJ40 electronic failures are caused by dry solder joints, A good soldering iron is an essential piece of kit for an XJ40 owner.
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Fylingdales in North Yorkshire does indeed transmit at very high power at or very close to the keyfob frequencies. Amateurs living in the area are restricted from using parts of the band.
I've parked within a few yards of the aerial and not had a problem with the car at all.
The spy network you refer to may well be Menwith Hill, also in North Yorks, and they certainly seem to listen to every word spoken and email sent. I'm not convinced this was why CE emissions regulation were made as the site is in a dip and all the aerials point to satellites and possibly our microwave link towers.
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The satellites I mean are European ones which watch the surface of the earth, and log all transmissions or look for them. All mobile phones sat phones etc... Of course I have never seen it, only read convincing articles about how it is used in wars.
It all reminds me of a time I went to Sytner BMW dealer in Nottingham (there old place) there was nowhere to park, so I parked at the rear in down town St Anns and could not get the remote to work for love or money and had to lock with the key. Ran to the parts dept. dodging bullets and ordered the part, ran back, remote still wouldn't work. left the scene. I replaced the remote battery thinking it was a gypsies warning. Returned to pick up the part some days later, parked in the same place, no remote again! Never had a problem before or since, so I wonder what was happening? I did wonder if someone had some sort of jammer in the onlooking community housing flats. Having said all that I can't see an immobilser being tripped while the ignition is on. The logic used in these systems is pretty thorough.
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As a complete aside, i walked back to the car and a thunder storm broke. The car (Skoda Octavia) wouldn't unlock on the plip, and i had to use the key. Once the storm passed, the plip worked fine.
Rather than radio waves, could it be electricity? Did Ashok park next to a substation? Does the electronics go kaput when you drive under a pylon?
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I remember having a presentation from Lucas (or it may have been Smiths) on a common bus system specifically aimed at cars in 1968 or 1969. At that time they had problems with hardeneing the system against the interference experienced in a car enviroment at that time. IC technology was pretty rudimentary, particularly for driving high currents.
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pmh (was peter)
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The points in this thread certainly highlight the problems or drawbacks caused by having so much electronic content in modern cars.
In March 2003 I was visited by the Vodafone install engineer to fit a hands-free car kit in my new Mercedes C220 coupe.
As soon as he realised that I had an Ericsson cellphone with (2.5 GHz) bluetooth link used for the hands free he informed me that , for a new Merc. I would have to swap the phone for another make and rebook the car kit install.
I had to swap the phone for a Nokia one as did 3 of my colleagues who were in the same boat. Apparently Mercedes had decreed that bluetooth linked phones in their vehicles were verboten !
I wonder if this was because of a known interference problem or whether Mercedes were just being over cautious.
Chris Muriel (G3ZDM), Manchester
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Part of modern car design includes RFI and High Voltage testing.
I think its VW that has a high voltage/rf lab where they drive cars around in severe electronic circumstances.
To answer mare tho they have yet to find a brave worker to open car doors while simulating lightening strikes.
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TourVanMan TM < Ex RF >
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There's also an EMC/EMI lab at MIRA where the entire vehicle can be irradiated to see if it still works, or measured for the interference it produces.
Number_Cruncher
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before any electronic or electrical item can go on sale in the EU it has to go through a series of EMI/EMC tests. The pass limits for these tests are, as with any other test, somewhat arbitrary. They are set so that they are unlikely to cause or suffer undue interference.
As we've all got radios that make a series of clicks just before a text message is received on our mobiles, its obvious that sone interference still occurs. There's a possibiiity of any electronic system being interfered with if the interferring signal is large enough. There are some very very high power radar systems out there, mostly used for military purposes.
I'm not up to date with automotive electronics but having the engine controller on the same bus as the ancilliaries sounds like careless design to me.
If some data on car models and locations of them cutting out can be collated then it shouldn't be too difficult to find the reasons behind these events. Without this information, all we can do is speculate.
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I read often, only post occasionally
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>>I'm not up to date with automotive electronics but having the engine controller on the same bus as the ancilliaries sounds like careless design to me.
On the later Vauxhalls, there are, IIRC, three CAN buses for high speed devices, intermediate, and low speed devices - data can be passed between the buses at the point where they all meet, the so-called column integration module.
The high speed bus is particularly prone to problems caused by poor or corroded connectors, and incorrect termination, which can cause unwanted reflections along the bus.
I think that CAN is a bit of bodge in the way that it has been implemented, I have seen that the error rate for signal transmission is not small.
As I've already seen some dealers really struggle fault finding with these systems, I dread to think how the independent sector is going to deal with them, without manufacturer's information or tools.
Number_Cruncher
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