CAN BUS testing

CAN BUS testing


hi guys rod from Tokyo just want to say the method I use when I’m trying to diagnose a can bus fault so I’ve just got a hold me vector here come from another shop and I just put my can fifth box onto the DLC and I’ve connected my own leader two pins six and 14 on the bus with the battery disconnected and then see here we’ve got the names of 1.35 now both you guys probably know that we should be looking at 60 ohms we have two 120 ohm resistors in parallel so we get 60 ohms what gets too confusing sometimes if you have a look you we’ve got a pretty elaborate sort of a wiring diagram here we’ve got we got being in Keene so we got a beer each vehicle area network and the controller area network so only one concern yourself with the the high speed can network so first thing I do to make life easier is all when they get bit complicated I like to just get it right down so what I’ve done here you can see I’ve removed all the van modules from the system so now what we can see is x1 is a DLC we can see it goes up through a module and then we’ve got an opportunity depending on whether it’s got a stability program or not and we go through another module and we’ve got another one coming off it and then we’re going to go down to the UCM so we know we’ve got a terminating resistor in here and after the dlc this is our our steering wheel control module so that’s post most likely being the other end of the bus we’ll probably have the termination resistor in that one as well so we’ve got one prints three five irons you can see they’ll react that the bus is going on this is the ECU then the next one daisy-chained in is this one here which is la BS so what are we going to do I’m not going to bother pulling the – apart and looking at steering module or any of these other modules that are hard to get to I’m just going to go straight to the ABS because I know it’s got to go through the ABS to get to the ECU and I’m just going to pay attention to where my arms go when I disconnect the ABS module so I’m just going to plug this here straight away we go to 124 ohms so we’re connected to the dlc and we’ve got now got one termination resistor in play so i now know by just doing that one unplug i now know that my fault my short is somewhere from the abs to here so i’ve already just by unplugging that one plug i’ve proven out all of this all the way up to this point so all my testing has to involve me out is just from the ABS unit to the ECU that’s the final part of my test which I’m going to perform later on today so you get them to set on that but I’m sure with all of the you’ll see that there do those two marks on that loom there you can see if I get in the right spot I’m sure we’ll probably find some damage from some rats so yeah I just wanted to show that that’s just a quick method I use just to quickly and easily get to the heart of the problem we narrow the wiring diagram down make it nice and simplified and then I try to find something that has a straight through connection typically the ABS modules a good one find somewhere halfway through the bus break it opened and then I can determine whether I’ve got to go this way or whether I got to go this way I hope that helps some of you guys I’ll catch us later bye


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