Network Communication Testing: K-Line, Serial and CAN Bus

hello everybody in this video we are going to talk about some Network communication testing and so I've got a scan tool a breakup box picoscope we'll look at two different types of network communication that are commonplace this particular Nissan has K line serial system for its data and then we'll look at a canned system on a newer vehicle as well so here we've got a handful of tools that we could use if we were going to look really closely at Network communication one of the great tools to do that process is this thing here this is a breakout box and so the other end of this cord is going inside the quest here it's connected to the data link connector it provides me a set of pins all sixteen of the DLC where I can make connections and then the other cool upside to this particular breakout box is that I get an LED light around the ones that have activity at the time so I can see that I've got power into it I've got a good ground at these two ports in sixteen has got constant battery and then I've got another port at the end here so I can hook up a scan tool so I'm gonna hook up my scan tool and set this aside and so when this is hooked up and things are going you can see that there is some activity I'm gonna go ahead on the tool go in my vehicle history and get the quest selected and so one of the easiest ways that we can create data flow and data transmission is to go on a scan tool and go to the kids and live data and so here you can see the Kaline which is pin 7 on this it's got some activity as it flashes back and forth so now on my scan tool I've got rpm oh twos just some general kids and you can see that I've got activity here so what does that tell me where would I use this in diagnosis it helps me understand that there's a good connection on the data network data network faults have become increasing more common as we add more modules we add more lines for data and so with that increase in wiring provides an increased occurrence or chance that one of those wires gets disrupted we'll go a little bit deeper with some of those faults as we talked about can so one of the things I want to do is show you what serial data looks like so I've got my Pico here I'll go to a ground and I'll go to the K line and then we'll switch over to the screen and see what that looks like so here is our trace and waveform for this K line I've got it zoomed out pretty far but each of these occurrences that we see floating by our packets of information so anytime we have information that's transmitted within a serial system really any electronic data system like this we refer to those as packets and so if we go and pause this I'm going to go back a frame or two until we get one of the packets so we'll take a closer look all this packet is is digital communication right so because it's digital the only changes I've got in this waveform are on offs and so I'm going from 13 volt down to zero and so this is a full source voltage just switched on off and so the on off ultimately translates to zeros and ones which helps me translate that computer language so that we can communicate things like engine rpm or the ECT value the things that are on my schedule screen right now that information is all in this packet that you see on the screen at the automotive technician level we really don't look to understand exactly how to break these down if you really get into the engineering side of these things there is software out there that you can get where we could take this kind of information and begin to decode it to get to the point where we understand that exactly which piece of this snippet and packet is RPM and so if I was developing maybe a a plug-in unit that would display rpm on the dash those are things I would need to know right as the engineer developing that as an automotive technician typically just looking to restore a vehicle to fix a problem that has impacted operation I'm not generally going to go to that level and so the things that I do want to look for is the technician is the voltage that I'm working with do I have a full source voltage here am i going all the way to zero here because those things help me understand basic electrical faults and occurrences which typically are the things that bring me trouble that if this Kaline signal was to get grounded or had some kind of resistive ground it may change that voltage and bring it down those kind of partial voltage changes are much more of an issue in kanne systems and we'll look at kind of how those are developed those are a bit different but again with my Kaline kind of set up like this I'm really looking for kind of a go or no-go situation the other thing that helps me with the Pico scope is that I can look at the main data bus to the ECM like every we're doing here and then I can look at it for other modules so depending on what the daisy-chain of wiring is that can help me understand where I need to find a fault so if we had a vehicle that had a serial communication fault so say we had a you code that was looking at a particular module for lack of communication one of the things that I really need in order to understand that sequence and make determinations about where to look is how that data bus network is wired and so a lot of data best bus networks are put in somewhat of a daisy chain where the main line of communication goes from the data link connector straight to the ECM and then other modules down the line are connected kind of on the other side and their own clusters so a diagram like this can help me understand that and so this particular ones got the data link connector down at the bottom we're working with pin 7 on our breakout box and so we could track that up that's got a direct line to the engine control module and so if I had a you code for the engine control module to say the trans control module I begin to look at where are these connected and I see pretty quick that the serial communication lines are separate from the K line that I'm using on this breakout box that's an important thing to distinguish because checking the K line on this breakout box is not going to help me with that fault so finding the roadmap in the the daisy-chain of this network on any particular car there's really a critical piece in trying to diagnose communication faults so if we wanted to interact more readily with those other lines that go to the trans control module you'll see that these are connected right so the serial communication lines for TX and rx so that's transmission on the TX side receiving on the rx side and so serial communication uses one line to send out one line to receive so on this one I could go to the receiving line is pin 13 on my breakout box so if I come over here and I'm gonna move this pin over to 13 we'll come back to our Pico scope and so here we've got some really small piece of pieces of information coming by what we'll do on the scan tool is see if we can make that more prevalent so I'm gonna go on my scan tool and go ahead and select data within the transmission control module then we'll go back to the Pico scope and we'll see what we've got here huge change in communication in activity I need to turn off my auto scale here so the screen is really having a hard time selecting what to look at because I had it on auto we're gonna change that we'll kick it over to a 10 volt scale and we'll look at more time so that we can see what's going on so I'm gonna go while that loads will notice there's a big difference in this serial communication line versus the K line that we saw on the breakout box at the DLC Lumpkins seven this one is only running at about three volts which is pretty typical serial communication is a low voltage communication and so it utilizes a separate lower voltage to make that happen alright so right there you can see this is activity from the scanner trying to make contact with the TCM and if you notice I gotta go way down here to see what was going on with that the transmission rate was quite high on those alright so here's my schedule I switched modules trying to communicate here with the ABS module and so you can see a lot of activity that's taking place we'll go ahead and pause one of these and zoom in so we get a closer look so again this is on a low voltage scale it is still digital communication so here this was some communication with the ABS module so we switched over to one of the other modules on that daisy chain and from here looks like a lot of noise I found that it can be challenging to get a really clear picture of stearic communication with the pico scope some of that could be my setup some of that could be the way that the breakout box is developed inside and so it's typically quite noisy there's some active filtering things we could do but for us at this point it does convey the idea that those lines are carrying communication and so I can see that there's activity this was a result of me using the scan tool to ping and kind of summon information from that module and so I can see that response all the way through the whole network and so that's a good sign for us if we were chasing some kind of communication fault alright so we've switched over to the 2014 Silverado I've got a similar thing set up here from what we did on the quest the biggest difference in the Silverado on being that it's a newer vehicle most vehicles post-2008 pretty standard to have can communication so controller area network communication and this is a different form of communication that utilizes a high speed and are a high and a low and it is a much higher speed or higher rate of data transfer the good thing for that is that because the sophistication that we're adding to all these modules and systems there need to communicate in real-time with large information packets as increased and so can has really satisfied that up to a point and so we'll take a look at what can systems are designed to do and how they communicate so on here I've got a handful of things plugged in I'll move some of them so we can take a look so if we look this breakout box is really great and that it's got a lot of notes and so standardized can pan outs you can see some of these say of sae and so that tells me that that's a standardized connection and so six and 14 are the typical kane communication pins on a dlc they're the standardized pins and so six is the high and then 14 is the low and so if we start with that i've got two channels going on my picoscope I'm gonna go ahead I've got both my grounds just stacked together real nice thing about picoscope connections here and a lot of scope connections I could piggyback those and so then I'm gonna go to just pin five my signal ground leave that connected as my reference and then my blue is my a channel red is my B channel I'm gonna go ahead and put my a on the low side or that I'm sorry the high side of things which is pin 6 and then low side which is 1014 and so now if we go back to the screen we'll get this zoomed in so here we've got communication happening I've got a scan tool hooked up here just doing live data so we've got some things happening on the network some extra communication we get these pulled apart we'll be able to see each of them so can low and high train made the same information packets just at different voltage values different voltage levels the reason for this redundancy is to help prevent any kind of electrical fault you know a resistance in open circuits a short-circuit if any of those things were to occur then we could potentially lose one or the other and still have functionality versus if I lose all communication with most vehicles a network that is open circuited will results often in a crank no start or no prank so that's where we see some issue with network faults is when we get to that level but if we just had a fault code for so a you code or some kind of communication fault this would be a great test for me to do just to see where my voltage values do I have consistent packets and typically I can learn some information from that so on this and sometimes difficult to get clean values alright so we're back on the screen here we've got our high on or low we'll get some of that separated a bit so that we can see better I'm gonna go ahead and turn each of the channels up to 16 bit resolution just to give us a little bit more vertical resolution and so here I've got these laid in there laid on top of each other and there's a trigger over here this my yellow dot that's my trigger to kind of keep these indexed and keep a flow that's occurring and so I'm gonna move and I'll split the screen a little bit here and we'll pause it so one of the challenges that I've had with this breakout box is getting a really clear-cut signal and so this one not the best example but I do have some fairly defined on offs which is what I'm looking for candy communication is a digital form of communication and do I do expect just to see on/off switching that helps transmit those packets of information the other thing that I'm going to look for on these is that the low and the high near each other I should see this repeatability like this as I go through that transmission if we go pull the example waveform that picoscope has that'll save us some time from chasing their connection issue here this is a better example of what we expect to see and really what I think is occurring on this truck I'm just having a time before time getting the connections without noise and interference so here you can see really sharp on offs very consistent voltage values at the top and the bottom that's critical and that's important and so if I was looking at this from a diagnostic in that's really what I'd be looking for and so on this particular chuck the other thing I wanted to show was how these things are put together and some of the different data networks that exist on it so this here is my data link connector these are the two pins we hooked up to so I've got six and I've got 14 those go to splice packs and then go over to these two wires and so on this particular truck this is the low speed can I take that back this is the high speed can excuse me and you can see all the different modules that it links together one of the other unique things about cam being that it's a two wire communication those wires are actually tied together with a resistor at each end we refer to those as the terminating resistors and so I've got one down here terminating there's a serf high-speed bus and one here at this other end the low and the high and then run in parallel through all the modules to connect them together the good thing about this is that because they have a terminating resistor if this wire was to get shorted to a power source that resistor should help us save some modules the other thing that is great from a diagnostic and is that if I've got two 120 ohm resistors wired in parallel I expect to see 60 ohms if I put my o meter across that so let's switch over we'll set up and we'll take a look at that test okay so I've got my book my o meter set up and buy two leads my breakout box is still connected to the truck I'm gonna go put one lead on pin six I'm gonna put one lead on pin 14 so I'm across my low and my high speed and we can see there I've got just about 60 ohms worth of resistance and so that's a good sign that shows I have connectivity between pin 6 and 14 to both of those terminating resistors and that tells me that the general health of that wiring is pretty good this is a good short test to do if I had a network fault just to confirm the viability of the operation and then from that point forward I would have to go on to individual modules and do checks from there there's some really cool tools that exist for doing those checks one of the cool tools that exists for doing these kind of checks on the general motor side so specific to this truck general motors develop this tool called the data bus diagnostic tool it's part of the GDS - kind of MBI platform and it allows us to connect with my MDI and basically ping individual modules and it will emit an audible sound based on what's happening and so the good use for this tool would be that I could set this up had it ping all my modules and see who can come back with a response and who can't and so on a vehicle that has a lot of different modules especially in daisy chain or a gateway that serves many modules it gives me a quick rundown of who can communicate and who can't and then I can create a diagnostic plan from that to say I only need to spend my time on the wiring and tracing of this particular module and so trying to cut down on just the physical time of tracing wires for communication faults between the dozens of modules that exist on a lot of vehicles so that's just short rundown on data communication and some of the practical testing we could do just to ensure that we've got good connections and some viability for our network communication I hope it's informational hope it's helpful thank you

Channel: Adam's Analysis

Views: 79,846

Keywords: parkland college, automotive, training, champaign il, picoscope, obdii, network communication, information bus, data line, serial, CAN bus, k-line, testing, diagnosis, breakout box, snapon, solus edge, adam karch, education, how to

Id: m9SOBEzwio8

Length: 20min 8sec (1208 seconds)

Published: Wed Apr 29 2020