CAN 101

[Music] welcome to another simply Diagnostics video thanks for watching yeah today we're going to take a brief look into some networks control area networks communication networks we're going to try and demystify them a little bit and simplify it down there's a lot of people that get confused about car networks what they should be looking for how to test the systems and common symptoms of a cam network failure so with this video we're going to run through and try and sort it out for you to simplify it and to you know debunk some of the myths and give you some pointers and tips for testing it hope you enjoyed the video well first of all we'll show you this at all well we've got it set up we've got a 2012 Hyundai i20 they've done a vehicle there's nothing actually wrong nothing wrong with the car we're just using it for test purposes today we've got it set up on a battery support unit gys wash 100 amp mm that's just to maintain battery voltage from last time oh it's on this caracal the battery we've got the engine ECU at the back with the cover already off it and so can get access to the wires for testing a common ground for me scope and basically what we do him I've got a dlc breakout box this under the cable goes to the dlc in the vehicle and then i've just got me katie that's what it gives me easy access to all the things on the dlc without having to scrub all underneath the underneath the dashboard simple DB om for taking basic resistance measurements and voltage measurements we've got the kts we've got the two-channel scope for the kts Hawk taught a lot of people say well I am got a pica wall I've got some nice cam - I've got a snap-on scope or anything like that and a being asked to do a video on using the kts scope so we're going to use the kts scope for this one today so we've got me camera got me a big screen set up with the relevant information so we can see it on the big screen there's a picture of the DLC connector you can see top left pin one bottom right pin 16 the pins we're interested in today 6 and 14 6 being the high speed can line 14 being the low speed can line and then we've got we've got the very self that we need it and we've got the laptop over there for the kts yeah so that's all we need all we really need a basic scope it doesn't have to doesn't have to be a peak or anything like a basic scope breakout box DB om battery support and somewhere to access the network and that's about where I saw looking in the 16 pin connector obviously this isn't it this is a drawing of it courtesy of all be detested comm like say the depends really interesting in today up in pin 6 which is the high the high side of the cam Network and 14 which is the long side and the single wire networks UK line will be on 7 and your L line will be on 15 16 battery positive or should be chassis ground 5 should be signal ground but like I say the ones we're interested in today 6 and 14 so the i-20 that we're looking on today I can't get full a full Network diagram for that without going looking for it but one of the things that you'll see is oK we've got the we've got the fuse box we've got the the data link connector this is showing two datalink connectors look - we've got the datalink connectors and then the ABS control unit down there and what you can see is all the cam buyers see the can lo is on the blue can hi is on the red wire and all the cameras so this twisted pair that twisted pair that twisted pair they're all the same colors so normally all the wires on a can network all the can Heil they won't call it all the can lo will be another color mm and it's normally the same right the way through each can network and then we've got a bit bit of basic information here from all data on our on our high-speed coming at work to terminating resistors 120 ohms each they're integrated into the PCM and BCM so that's the engine computer and the body module since both hundred and eighty 120 ohm resistors are connected in parallel the total resistance is 60 ohms measured at the DL say if a control unit is disconnected from the network 120 ohms must be present between pin 6 and 14 on the DL C so here we've got a wiring diagram of a Vauxhall Astra you can see we've got the the DL C here pin six can high 14 come low you can see all that they come the twisted pairs the high-speed can is green the low speed Kenny's is white and all we've got with the key off we've got an actual what we call the physical layer and it's two pairs of wires going to each module account high in a can log going to each module some of them go through all the modules and a bridge now others just go straight to the dlc so what we what we're looking for before we do any sort of scoping or measuring or anything like that the first basic check we need to do is to make sure that the physical layer as in the route between 6 and 14 right the way through the vehicle is intact the the physical layer is actually intact and it's measuring 60 ohms between 6 and 14 if it doesn't then we're looking for an open circuit a short to ground something like that or module disconnected so that's the first check that we're going to do so so first thing we're going to do we're going to do a check of the physical layer we're going to use the Pico breakout box and a DV om I've got the Pico breakout box plugged in into the DLC in the car to me meter arm can you see that okay yeah so obviously the one they're showing open circuit I've got it on a 200 ohm scale put poseability check put the leads together just to check that me meters okay and there's ball part that's good enough for what we're doing then all I'm gonna do now pin six on the box it corresponds with pin 6 on the DLC and 14 correspondence with 14 on the DLC so I'm gonna do should be me two leads into that and that should give us 60 ohms which it does that about can you see that let's just zoom in so you can see the neat it know 60 60 1 point 5 ohms and what I'm gonna do now all I'm gonna do is I'm going to unplug the engine ECU which is over here where me handle this I'm going to unplug that and you can watch the meter and see what happens to the meter okay so 60 ohms and put the engine ECU which is where one of the terminating resistors is located and it jumped up 220 ohms so that tells us that in complete and one of the terminating resistors is out of the picture and bear in mind this check is done with the key off nothing on the vehicle asleep so that's one of your first checks if you're reading 120 ohms between 6 and 14 you've got a break in your physical layer so what we can also do now is we can short one of those to ground so we just get another we'll get a jump lead now doesn't have to be anything fancy or posh all I've got is in two four mil bananas and what I'm going to do I'm gonna go to me chassis ground which is pin 4 and I'm going to short the high-speed can out that's like before I do that I'll plug the modules back in I put the engine ECU back in so we can see we've got 60 ohms again so we've got 60 ohms back in I've got one way to me chassis ground and all I'm gonna do is short it to ground sell the resistance doesn't change no high speed the same thing the resistance doesn't change okay but what that basically what that tells it is we've got 220 ohms resistors in parallel and our physical network is incomplete it's sorry and our physical network is complete and the short to ground will make absolutely no difference to the resistance in the circuit okay now what can do is I'll turn the key on you see the minute I turn the key on what happens the network goes open circuit and this is why we do the test with power off turn the key off money goes to sleep the meter will drop back down sometimes it takes a minute or two for the network to gautham go back to sleep but this is why perform these tests with the chaos vendors and the vehicle asleep you can't check a physical network with power going through the circuit there you go the net where it's gone to sleep and we've gone back to 60 ohms okay what we'll do now we'll have a look at the voltage levels using a multimeter first so we change our meter now to DC volts 20 volts scale due a plausibility check with our with our meter so it's a battery ground chassis ground and pin 16 which is positive okay so there's our battery voltage so we know our meters okay we'll leave the ground in there and we'll check will check pin 6 verse the can high no voltage on that I'm 14 no voltage on that we'll turn the key on soulkey arm on the can low we've got about two volts two point one volts something like that and on the can high 2 point 6 volts is there's about half half a volt difference using a using a multimeter so they're they're good checks of all you've got is a multimeter good good checks just to check your physical layer and to check the rough voltages with the DB RM okay let's see if I unplug the engine ECU no actually I'm not going to do that not with the key on mmm yeah come dig I can do all right so weed the keys off just leave it a second or two so with the key off you see the battery voltage drop down straight away so with a 1.4 eight on the can low with the key off to 2.8 on the can high with the key off but the network is still alive it's just not not powered up the same so what we'll do now we'll unplug the engine ECU and see if that voltage changes doesn't the engine ECU unplugged key off we've got zero volts PM 2.5 on the can high and 2.2 on the can well so just simple tests that you can do the DB LM if you haven't got a scope came back on physical layer repaired 2.1 honking low 2.6 on counter-ied half a volt difference using a DB OEM and then if we go on to the skull you see they're using they're using the skull I've got the red channel on pin sexcam high and the yellow channel pin 14 can lull I so looking looking at there at the boss go we've got the tube both both channels are on both on a voltage measurement which signified by the U and both the set to DC I've got them on a 10 volt scale and just so it makes it smaller on there on the video and you can see that with the key on we've got two signals count high income low and I'm basically what all they're doing they should mirror each other which the other polls that you can see so so looking at this with it with it paused you can see they're the two signals mirror each other there's a little bit of interference obviously because we use in we using a Bluetooth scope so there's going to be a little bit of interference on there we've got a two hundred none none also is that nanosecond or microsecond might be microsecond setting and what we can see is the can hi you forever get there you get the actually what you can see is it but just pause it make you seize that can hi is going from about two and a half volts it's a three and a half volts and come low he's going from one and a half volts to two and a half volts on the scope and all they are is they're mirroring each other so we'll leave that running now and let's see what happens when they disconnect the engine ECU and we lose one of our terminating resistors so I'll leave you focused on the screen and I'll just go and unplug the engine ECU with our engine ECU you can see that the voltages have changed a bit they've gone a bit broader for one of the terminating resistors unplugged so we now we're now touching nearly four volts - now volts - nearly four volts and just over one volt - about 2 point 7 volts something like that so this is change in voltage levels plug the engine ECU back in everything's live and you can see those voltage levels have dropped back down and it's a much tidier signal I'm going to show the can high to ground and let's see what happens to that signal I should be able to do it with just a normal wire but I'm going to use the test light just for safety so I'm now shorting the can high to ground you can see what's happened there to the signal take it out a signal returns now I'll do the same thing we can low or short that to ground see what happens there take it out and the return so you can see the count system is a fault-tolerant system and what I'm going to do now I'm going to short it to the battery positive and let's see what happens there so can high - battery positive that flows because of the trigger can low it's a battery positive that froze so let's let's just get rid of the trigger let's get rid of the trigger and see we can I'll just put the trigger now on auto level we'll do the same again cantaloupe the battery voltage it's gone off the screen so let's let's increase the increase of voltage so with both there with them with the scales drop down now I'm gonna shorten to battery voltage so first of all can high to battery voltage it takes the whole thing go take it by three voltage that's what you can lo looks like shorted to 12 volts it's bringing that basically spring raising the voltage level to the whole so you can see you've got a short short to power that's what's going to happen to you network and we go short to ground that's what's going to happen to network and then the other test we can do is if they short to each other okay so I'm just gonna stick that in there and now I'm going to short them to each other and that's the network surety to each other so that's the high shortage of the low if you had a twisted pair with corrosion and they were bleeding off into each other take it away and we've got a normal count signal again so there we go there's cam 101 in a nutshell nothing really exciting about it nothing tricky about it it's just a really really basic simple system yes oh there yeah that's that's basically that's can't systems in it in a nutshell power off 60 ohms between 6 and 14 you can do the measurements with the DB RMB on 6 and 14 with the power arm and we look at it about 1/2 of all difference in the wires and if you've got one e terminating resistors out of the picture it'll measure 120 ohms your two signals should mirror each other nice square patterns that mirror each other no big dropouts or anything like that like say the our fault tolerant network so that can be shorted to positive shorted to ground shorted to each other and the minute you restore the actual physical layer it returns so it's it's a this really is this there's no great science behind this you're literally all you're looking for is nice no study square wave patterns packets of data 60 ohms with power off for a complete network 120 you've got a terminating resistor out which is normally energy management an instrument or energy management and body module that's that's normally where the terminating resistors are nothing there's that there's nothing to it it's very very simple very very simple so there we go I hope you enjoyed that brief insight into camp we're gonna we're gonna get looking at it and look at some real real world real life in camp faults but the basic principles still apply and if you've got you know a baby can grasp them then network network faults are not hard so hope you enjoyed that don't forget to leave a thumbs up if you did thumbs down if you didn't and if you do leave us a thumbs down don't don't forget to put a comment in to tell me why you didn't like the video I can't get better if you don't tell me what I'm doing wrong thanks for watching and thanks for watching the video if you liked it don't forget to leave us a thumbs up hit that subscribe button if you didn't like it give us a thumbs down put in the comments section below let's get conversation started we've also got ways you can support the channel now if you look in the links below patreon buy me a coffee calm and they direct pay polling thanks for watching and thanks for supporting the channel you're awesome

Channel: Simply Diagnostics

Views: 126,745

Rating: 4.9036145 out of 5

Keywords: DTC, Automotive Diagnostics, Simply Diagnostics, Automotive Training, Picoscope

Id: EJibx-YjCcI

Length: 26min 41sec (1601 seconds)

Published: Sun May 13 2018