2012 VW Jetta No Communication with TCM U0101 (part 1)

Vehicle is stuck in park, check engine light is on and there is no communication with the transmission control module. In this video we will be troubleshooting the CAN network using a lab scope. In Part 2 • 2012 VW Jetta No Commu... we repair this vehicle and are surprised by what we find.
Here is the link to Tommy's KZbin channel
Positive Lead Diagnostics / @positiveleaddiagnostics
Tools used
- AES LineSPI (SMART BOB)
www.aeswave.co...
- Test Drive Test Leads for the Snap-on VERUS
www.aeswave.co...
- VCDS® with HEX-NET® Pro
www.aeswave.co...
Related videos
- Poor running, flashing CEL, no codes (bad computer ground) - Toyota
• Poor running, flashing...
- How to test a computer ground circuit (Audi)
• Intermittent no start ...
- ScannerDanner Premium Audi S5 series
• Video
• Video
• Video
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdan... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@PappaDanTrucking]

Great job guys! you showed the way many of us have to learn these systems. This just shows the lack of info that the engineers don't share with us as real-world techs.

[@tommyljungdahl5107]

I would say the best way thinking about the Gateway in a Volkswagen network is comparing it to an interpreter. The main work the gateway has is making it possible for different types of Can talking with each other. If lets say the door wants some information from the engine it can not ask the ecu directly due to not using the same type of network, the door uses a low speed can called convenience can. Therefore you have a gateway that translate and sets priority. A good tip for using Volkswagen style diagrams is using them in the computer and use CTRL+f to find what you are looking after (for example tcm just open the correct diagram and write j217). Sorry for not writing good in English and making this understandable.

[@ScannerDanner]

Thanks for the info!

[@kirkabrahamson1148]

I think this is one of the best vids yet. While watching I'm thinking this is gonna be complicated then knowing about the can bus resistance and thinking to check powers and grounds what else? It cant be that simple. So good watching you guys bounce ideas of each other and take the diagnosis a step further trying to understand how the system functions as these systems are constantly changing. Judging by the resistance difference at the tcm compared to the aldl connector it seems there may be separate can bus lines for different systems but all terminating at the gateway? There is some awesome talent now available through you tube with yourself Tommy Ivan Eric O and now Keith coming on board. To be able to learn and apply these techniques like this is awesome. Respect.

[@stephenmarshall5302]

I work for audi 8 years now and I completely agree with the current flow chart being trash, I suffer the VAG stuff daily but it becomes familiar in a way. Really impressed with danner I like the raw side job approach to these videos because they are real life situations. Thanks for sharing this knowledge I will be using it to become better

[@ScannerDanner]

Thanks so much stephen marshall!

[@MiracleMAX]

From the research I have done, the termination resistors are designed to stop ringing in the data line - sort of echoes that would make communication impossible. Think of the ringing on an ignition coil that has 'back EMF' after the spark burn time has completed - you get that wiggle that is an indication that there is reserve left in the coil, ensuring the coil is in good condition. So the resistors stop that ringing that would echo back and forth over the BUS line and seriously mess up the actual communication. Testing the resistors is one of the basic tests of the BUS line. More of us Lecturer/Tech/KZbin creators are making it easier to diagnose problematic vehicles. It is the best way to share the knowledge we have gained over the years.I have been a Tech for 34 years, a Lecturer for 14 and KZbin creator for almost 2. (Sorry for the plug....) Great to see you guys working together. Keep up the good work!!

[@TheDdBob]

VW, all the Euro's and especially Land Rover NEVER give enough info. They only give the bare minimum. In the case of Land Rover they always refer to their OEM scanner ( testbook) for tests, as vague as "consult the testbook". it's refreshing to see knowledgeable people such as you two still struggle and struggle with " I think it might be the TCM" Your videos are always the best because they are real world, you have a humbleness and you don't candy coat it like so many do as they try to make fixes look so easy.

[@MrBugzzie]

Exactly what I have been struggling with on my 2011 GMC Duramax in regards to Can, Serial networks ,this video is very helpful and I am glad I invested in the actual service manuals when I purchased this truck ,wiring diagrams ,explanations of networks and the other modules involved with any other module .Watching you guys really helped me understand what it is I am actually looking for !! Still need to absorb how to utilize measurements of terminating resistors with the use of DMM Great job guys

[@heatherrhodge2588]

Ya know that stuff shld come free when you purchase a vehicle! It's BS having to pay almost $100 just to get your hands on info about a vehicle you OWN! It took me over a mt to find PART OF a service manual online thx 2 someone generous enough to post a download link. Def no thx 2 the Acura dealership who wouldn't even email me a wiring diagram & instead put me on "hold" (well said they were transferring me but hung up on me instead) & other times I called wouldn't do anything except tell me to get my car towed to the dealership! I'm unemployed at the moment so I couldn't afford to pay for a service manual much less pay the dealership to repair what I was able to fix for $5 once I accessed the info that's readily available to their mechanics!

[@dil6969]

Always excited when you, SMA or Ivan upload a new video. Whenever you get the opportunity, I'd be interested to see you go over push button ignition systems on newer vehicles. I managed to find a wiring diagram of my parents' 2015 Honda Fit starting system and was baffled by its complexity. There's nothing wrong with the car, but I was interested in seeing how these newer ignition systems work. Thanks in advance!

[@benjaminrich9396]

I've long thought all cars should have a full wiring diagram or at least a network diagram printed under the bonnet (hood, I'm British). I'm sure a lot of people (myself included) are liking these network communication case studies. great stuff chaps. it's adorable when Tommy comes out with Dannerisms like 'it won't get out of its own way'. :)

[@zfloz9895]

Most of the drivers don't even know how to change a wheel or to ceck the oil. :) Imagine how they look at a diagram? :))) But I woul love to see this on every car !

[@360quickshot]

I work at a BMW dealer and we have a lot of classes learning about bus networks and such. I think that this Volkswagen might operate their bus networks in a similar way. when you were using the breakout box to measure both signal and resistance I think that you were just measuring on the bus lines for the gateway. like on Bmws we have a gateway module. and it has a diagnostic can line just on its own two wires that only feed to the obd connector. so in that measurement you were only looking at that diagnostic can line and not the can network as a whole. the gateway module in our cars is Just a translator. we have a few different bus networks. (PT can, K can, most bus, PT can 2 just as examples) and each of these bus networks operate at a different data transfer rate. some are as fast as 10mb/s and some as slow as 100kb/s. But every one of these bus networks connect to the gateway and the gateway is a translator. So let's say the ecu is on pt can, and is sending data at 100kb/s and it wants to send a message to the abs module on the k can bus which is sending data at 10mb/s they aren't considered to be talking the same language. the message that the ecu wants to send must first go through the gateway module to be "translated" into the language that the abs is speaking. we also use different terminating resistors in our flex day bus. it uses 90 ohm resistors. and instead of having 2 in the whole bus. Each module has its own terminating resistor. but I feel his pain on the no info thing. on our k can network we aren't provided info on the location of the terminating resistors or their resistance values. fun fact though. we use fiber obtic cables for the data bus on our entertainment modules like amplifiers and radios. they are very easy to diag no communications though. the bus layout is in series. so you just add in a fiber optic loop at the module that you think is causing the no com to see if everthing else after it begins to communicate again. we have also started using Ethernet as a way of communication and for being able to program multiple modules at once.

[@AutoFocus-se]

That's right . I'm actually working on a BMW with a K-CAN problem keeping the car from going to sleep. A module is messing up the CAN Low signal. I just need to find which. Thanks for sharing.

[@ScannerDanner]

Thanks so much for the info!

[@franciscovera828]

junk cars

[@zfloz9895]

360 Good info in just one message, in stad of one hour + of video time. :) Thank's !

[@turtlezed]

Does NASA know about this technology? They might want to overcomplicate their rockets to achieve the same thing they did decades ago in the name of efficiency........now I'm just being cynical eh?.....all of this just to drive down the road........

[@alexbrophy6885]

Short to ground is 0 ohms, open wiring or resistor 120 ohms. Tip if you want to see communication you can open the door to get a bus message. Just some input love the video!

[@benjaminrich9396]

good tip on the door

[@unencumbered]

Alex Brophy Simple is always easiest and often best...thanks

[@Dasdembo]

It's not a VAG com its VAJ com😀

[@33798]

So great to see such wonderful diagnosis with manuals, thanks so much to you both. Got it Mr.SD and another automotive (positive lead diagnostic) channel in my list.

[@glenohara6563]

I went to a training night on these more modern can bus com systems when they first came to Oz. We were told the terminating resistors were there to take out the reflection of the can signals at the end like waves in a wave pool, similar to trying to absorb resonant frequency to stop it generating its own signal.

[@johnd8651]

Working at a indy euro shop the hex cable and vcds is literally priceless

[@HomieHektor]

When I was at Chevy, I never got used to the factory because I started off with a Verus thanks to you @ScannerDanner

[@mmichaeldonavon]

Paul. The two resistors stop signal REFLECTIONS at each end of the CAN. Just like in your house. When you have cable outlets in various rooms, those wall plug cable connectors should be terminated with twist on caps that have resistance. Usually 50 ohms Z - or 75 or 92 ohms of Z. Stops signal reflections the same way - "absorbs" that energy travelling down the coax (at 65% the speed of light :) so it isn't reflected back to your TV.

[@NabilChouchany]

Great work guys! BTW K line is the communication line: Kommunikation in german it was present for comm with the scantool, long before the can network

[@wbfog]

Great video like always! I've been teaching lots of network diagnostics to my students. Really nice to have some backup to confirm my teaching. I recently learned that on a 2015 Jeep Wrangler, the network is very similar to this VW, in that you must back probe the network to see past the gateway module. I tried pins 6 and 14 with the breakout box just as you guys did, but found these pins were for scan tool only.

[@ScannerDanner]

nice!

[@scottshoellhorn2524]

Just got done watching this one, love it. My 2009 jeep wrangler pin 14 and 6 pin of the diag connector go directly into the gateway/ totally Intergrated power module. Same thing, measures out at 60 ohms but no signal. I figured it was just used for communication with the scanner too. So I moved it to the power train control module and got the signals. I have also been burnrt too by the fuse deal that tommy ran into as well. Great catch Tommy! Here is what caught my ear!!!!!!!!. How many modules have just one power feed input???? From what I have noticed there always seems to be a keep alive power feed and a key on feed. That is the lesson I learned here. Paul and Tommy keep it coming, It takes real guts to stick your neck out. Thank you again. Scott Shoellhorn

[@Sam-lw6mx]

the gateway is usually used to communicate to diagnostic tool one side and to the other ECUs on the other side using two different communication networks. there is no physical link between the two networks

[@richardcranium5839]

my guess is they put a gateway to conform the european standards to work in usa

[@Nymi5]

Difference on the voltage at datalink connector is, the scantool is using higher voltage on signal then the data bus module in the car. Higher voltage at the scantool is used for the wake up the data bus module on some cars. Higher voltage is the scantool talking to car and the lower voltage is the car talking to scantool.

[@wyattoneable]

I liked the different camera angles. You did good at asking questions. That kept me on track and interested. Not having information is so aggravating. Great team effort guys! I'm subscribed to Tom. He's doing great work.

[@theadventuresofjavier8698]

scanneryoda,keep teaching excellence. wonderful to see a former student excel....your the best my brother.

[@annacav122391]

Terminator resistors are used to prevent echoes or reflections in the signal being transmitted due to some of the energy not being absorbed. A refection of the signal would cause noise or a dirty signal. They are placed at the farthest ends of the bus or network.

[@markd6637]

I'm a master Volkswagen Tech myself been with Volkswagen 14 years you probably could have used I wire it's a little better and I wish you pulled out the Otis scan tool yes the engineers they don't give out so much information but the next step would contact techline with your diagnosis and they would say put a TCM in it

[@MichhaelPhresh]

Need your help

[@chaseconway9679]

Can you help me

[@chaseconway9679]

Crank no start 2007 gti dsg PRNDS lights flash on dash

[@lobo5055]

Master tech wow

[@BG-gg9pl]

😂Good for you buddy! Call your tech line and maybe they’ll send someone out to do the diagnosis for you🤦🏼‍♂️

[@pinkpanter9242]

Gateway is used to join two different can networks. On typical vehicle you have two different can networks. 1. High-speed can - is using up to 1000 kb/s data transmition and is used to work with critical systems like pcm, tcm, abs, esp...etc. 2. Low-speed can - is using up to 124 kb/s and is used to work with less critical systems like for example car lights, indicatirs, door windows, alarm, inner lights, wipers...instruments...etc. For example the instruments are connected to low- speed can and it need to show engine speed. Thy instuments have to ask pcm for that data, but the pcm is on different network. That is way the gateway is used. It joins two different speed can networks. You can also have MOST network used for multimedia and it also need to comunicate with can .... the gateway is also used to join them.

[@ratchetrdz9113]

GREAT VID GUYS, RESPECTED, REAL WORLD TIME REPAIR ON A CUSTOMER VEHICLE, LIKE THE HONESTY BOUT THE TRUE ISSUES ONE RUNS INTO

[@patrickliverpool6487]

Always excited when you doing trouble shooting I learn alot from you Paul. Thanks to you

[@michaelfrancis3261]

love how you guys kept it real

[@DylanRabier]

Awesome video! First of all you and Tommy doing a diagnosis together 👌 I would love to see more on network troubleshooting. This gets harder every day in modern vehicles. Thanks guys!

[@ScannerDanner]

Thanks Dylan! As I learn more about these, I most certainly will. I don't think the network diagnostics are as voodoo as people make them out to be. And no matter which way you spin it, you are potentially going to be ripping a car apart to access all the modules on a crashed network, so you can unplug them one at a time. I think everyone is looking for a short cut, and I'm just not seeing it.

[@DylanRabier]

Think you're right Paul. There is no shortcut 😞

[@therealchayd]

In my days as an electronics engineer, we'd call something negatively affecting a multi-point differential signaling network as "shitting on the bus".

[@therealchayd]

Nice try, more chumps to add to your botnet.

[@nicknicu1787]

As much as people hate working on Euro trash,it's a smart design if you think about it. Otherwise one module can pull the whole network down and you would get stuck somewhere in the middle of the road. Motoyam82 has a video on a Nissan where the ABS module is causing the car not to start. Great video Paul! I can't wait for part 2! I'm subscribed to both channels and Tom is great! 👍

[@Mikesky10]

Nick Nicu can you put the link of te video you mention please?

[@ScannerDanner]

Got to give my boy Ivan some love for sure. I need to watch it myself so I can learn something.

[@baxrok2.]

Ivan even used the AES tool to check for shorts to ground! That versatility is why I was looking forward to watching you use it in this video. Thanks!

[@rharris5811]

Keith from Staten island had a Chevy van the other day with no com, unplugged airbag module and everything worked.

[@PineHollowAutoDiagnostics]

Actually it was a Mitsubishi! In any case the wiring diagrams were easier to follow than anything for Euro. Even the terminating resistors were shown in the OEM diagram :)

[@jackstevens9907]

Hi there guys. I know this is an old video so you may not see this and it may have already been mentioned but the reason you were getting different readings with the scope and multimeter when testing at the DLC and the TCM is because they are two different networks. There are multiple networks that are separate from each other hence the difference in readings. I hope this helps and apologies if it has been brought to light previously. Love the content guys, I’ve followed you both for years. Much love from a trainee VW Diag technician from the UK ❤

[@ScannerDanner]

For sure! We've learned a lot since this time. In particular when the DLC is wired to a gateway only. Thanks!

[@jackstevens9907]

@@ScannerDanner No, thank you. You have no idea how much I have learned from you over the years. I’ve been watching your content for the best part of 7 years. 👍🏻

[@ScannerDanner]

@@jackstevens9907 thanks so much! That's awesome

[@israelzunigamascorro9300]

Great video, thank you and I hope you continuing sharing your knowledge with us god bless you and your family too

[@voland4513]

Awesome.Paul.I just had read an article a week ago in Motor Age from Eric Ziegler about Can network and diagnosis and here it is, more from you. Thanks for the video.

[@RyansAutomotiveTV]

Great video thanks I made similar mistake a few years ago while trying to demo a scope checking can signal from the obd socket on a VW and was not getting any signal and only after checking wiring like you did figured it out Up to about 2004 VAG group did not have a CAN in the diagnostic socket and they just used k line to talk to all ecus on the vehicle And on the later ones they used CAN to talk to all ECUs but they still used Kline as well for engine As if the gateway is gone down completely you won't be able to talk to any ECUs except for engine as you can still connect to this through Kline

[@queez11ciara]

Awesome video bro... this would have had me scratching my head for a while man thank you for sharing this knowledge and know how ....

[@DanielGomez-jk6bv]

I just want to share an experience and advice I believe is worth knowing. If you work turning wrenches for any shop, make sure your personal tools are insured, don't assume the shop insurance policy will cover them in case they get stolen. I learned that the hard way. Almost $18000 worth of my tools were stolen and the insurance company just showed me the middle finger...of course the owner's stuff was replaced. Rather than doing something to help me recover my tools, after weeks of, at that ponit demanding to get the problem solved, he was kind enough to just show me the the door.

[@JOHNPHUFNAGEL]

Thats really messed up, you should have also got paid for your tools

[@DanielGomez-jk6bv]

JOHN HUFNAGEL ..that's what a good logic and reasonable person would do, fair if you ask me. Did I mention also not getting final paychecks?? Now is time to let government deal with him..

[@LynxStarAuto]

Daniel Gomez in what state do you work? Here in Florida, shops get away with murder. Years ago when I was working for a shop, the owner had a nasty habit of grabbing your tools and using them. Trouble is he would just leave them lying around. That was how he misplaced my Matco Infinium 18v 1/2 impact. One day I took a car on a test drive, and it left me stranded. He was upset about that and told me you are going to pay for that tow! Of course I said oh yeah? Well if we are going to be that miserable, deduct it from the 600+ electric impact gun you lost... Needless to say that relationship didn't end well. But it was fuel to the fire which eventually ended up in me opening up my own gig. Moral of the story don't take abuse from anyone. Live outside of your comfort zone because that is when we are at our best, and most efficient. The moment you get comfortable, you get complacent, and that is a deadly combination working against you.

[@DanielGomez-jk6bv]

Lynx Star Automotive... I am in Washington state. We as employees can get a fair amount of protection from laws... I personally made mistakes or broke components during repairs, a common thing that can happen. Many times I offer to pay for my mistakes, but I was told that employes should not pay for stuff like that. Any employer who tells you otherwise, can get in deep trouble. The problem with the person I worked for is that he is the most shady person, who never takes a blame for anything, but will blame his mistakes on everybody else. A lesson learned for my tool box... I can put lots of stuff in it, no tools in it! lol

[@bbmd2200]

The K and L lines are used for scan tool communication. K -line from module to scan tool and L-line from scan tool to module. Also, the gateway is used as an intermediate between the different can speeds: High speed and low speed. You can still measure the resistance of the network at the DLC with the gateway in between because from the DLC to the gateway is considered as the CAN C diagnostic. At least, that's what I understand. Also, the CAN Transceiver in each module, is responsible for the voltage difference.( 2.5 to 3.5 and 2.5 to 1.5).

[@ScannerDanner]

Great info! I have since learned all this but really appreciate the comment.

[@somerandomguy3868]

great video guys a look inside​ side VW way of doing things. my very limited understanding of the gateway is preventing me from having a hard opinion either way I'm leaning towards not caring for it only because I don't see any advantage to it yet great video

[@Pablo_Automotive]

great job Tom and Paul thanks for share this case is realy interesting.

[@markd6637]

What I believe those resistors are doing is stopping communication from going back to the other module as an echo if that's easy enough to understand the way I explained I don't know how else to explain it

[@tonyfremont]

Exactly, termination resistance (always at the physical endpoints) stop reflections from the high speed digital transitions from degrading the signal quality. The sad thing about this case study is that the TCM could probably be repaired by replacing one integrated circuit inside it. It might even be something as simple as a capacitor, resistor, etc (passive parts) on the board. Somebody will replace a $1 worth of parts and sell it as a refurb. Whatever happened to kill it is probably killing them on a daily basis.

[@rafaelgarcia-xk7eu]

Hey Dan, your M4 scope multimeter on your verus pro is removable and can be connected with the supplied USB cable for test drives. One lead, works great.

[@How2Wrench]

Awesome information. Appreciate your willingness to "learn the tool" on video as you go. Also love those continued Instructor/teacher relationships. How cool is it to see your student have such respect and do what you taught!

[@PaulysAuto]

So glad you guys made this video because there is so little out there to help guys in the field understand this subject area. Thank you for taking the time to tackle a subject that everyone seems to be still confused about at times! Both of your guy's channels are top-notch, wish you the best!

[@ScannerDanner]

Working through it with you guys is the plan. Thanks!

[@PaulysAuto]

ScannerDanner, well I cannot thank you enough for all the lectures and in depth analysis you put into your content. Filming your work has got to be difficult and time consuming. Further, you still have to fix the car! Having your experience and knowledge outlined in such a way that truly teaches critical fundementals is invaluable! Keep up the good work you guys, you deserve success for all that you are doing!

[@atari7001]

Termination resistors absorb "ringing" that occurs when power is quickly removed from the CAN line. The CAN line itself is an inductor that develops a magnetic field around it when energized. Inductors resist the quick change in current that a square wave produces, which causes the magnetic field around the wire to collapse and induce a secondary current in the opposite direction. This process repeats rapidly and is essentially a resonance which appears as noise. The resistors dissipate this energy before it can interfere with communications.

[@rsanchez5676]

Terminating resistors in communication lines are generally used two stop reflection of signals back into the communication line the signals will actually bounce back from the end of the communication so generally your terminating resistors are at the end of your

[@glasser2819]

TCM-ECU are on the same highspeed CAN-C The Gateway is to transcribe message accross different buses. All module on a specific CAN can reach each other directly without any Gateway. ✌️

[@ScannerDanner]

We've learned a lot since this video. Thank you!

[@Nabeelco]

Danner, I'm so freaking jealous of your Hex+Net.

[@JOHNPHUFNAGEL]

Thanks guys that was a excellent video!! Cant wait for more from you two..

[@IMFDB]

high speed data comm faults is one of my favorite things to diagnose and i specialize on gm products. it appears unfortunately Volkswagen does not have main wiring schematic that shows a high speed lan schematic like gm does. basic principle is 120 ohm resistor on one end, usually an engine control module and a terminating resistor built into the body harness or a body control module on the other end housing a second 120 ohm resistor. both working on a no problem car using ohms law is 120 ohm divided by 2 modules = 60 ohm of resistance at the dlc pins 6 and 14 with all modules asleep. add usually 1.8 ohms of resistance for the 20-30 feet or wiring looping around in series. 61.8 ohms is a very common number i see on a majority of cars. i think 68.8 ohms is way to high even though Volkswagen states 60-72 ohms normal. most common things i see disrupt this data comm network is aftermarket devices usually plugged into the dlc that have to much or too little resistance and send electrical noise into the system. once in a great while i see other oem modules get internally shorted and lower the data comm resistance to lower than 60 ohms and cause intermittent loss of communications and symptoms are noted like no electronic power steering or harsh shifting and gm's stablitrak light. i've seen a 2017 silverado diesel truck with a lift kit have 47 ohms or resistance in the circuit and get's intermittent stabiltrak lights and codes state loss communication with several high speed modules like u0100 as history code. tracked it down to aftermarket speed controller manufactured by hypertech designed to correct the speedometer for the oversized tires. it is tied into the high speed data communication circuit and is causing all this mayhem. i wish i was there to help you diagnose this one. hope you found my insight helpful

[@timtec3000]

VAG wiring diagrams are horrific to interpret!

[@DJ-tn7vj]

Thanks for the insight

[@rickhayward4507]

Bro your cap is splitting with all that brainpower!! Love your work.

[@ScannerDanner]

haha thanks

[@killerguitars52]

Offboard Diagnostic Infromation System. Very different than VAGCOM. They both have their place but very different. VAGCOM is nice for quick basic settings, code pulling, output tests and non warranty related repairs. ODIS allows for diagnostic "test plans" to walk though difficult trouble shooting, component protection, login access to secure areas of control modules, coding, programing, key adaptation and various other "dealer only" functions. It also records diag logs to submit for warranty to prove failures and countless other functions. It is after all the dealer scan tool and lets you do everything.

[@teardowndan5364]

The CAN bus between the gateway and the scan tool is separate from the other CAN bus(es) from the gateway to everything else. Each network segment has its own termination resistors. What are termination resistors for? They dampen ringing (signal reflections) that would otherwise occur on unterminated wires and ultimately render communication impossible.

[@ScannerDanner]

So there are separate terminating resistors in the gateway specifically for communication with the scan tool? At least on this design.

[@teardowndan5364]

As someone else already wrote in comments, the 'gateway' here appears to be operating a bit like a home network router or switch. Each 'port' on the gateway is electrically independent from all the others and communicate through the gateway's software, with the gateway seeming transparent to most normal traffic. If you shorted out the ECU's CAN bus, you would still be able to talk to the gateway and whatever other systems might be on separate ports from the ECU. With the amount of comfort, convenience and other non-critical systems in fancier modern cars, it makes sense to split unrelated functions into separate CAN busses and use a 'gateway' to bring them all together so a failure in non-essential circuits doesn't bring the engine, transmission and other components down with them. You wouldn't want the volume buttons on the steering wheel to cause the ECU to shut down at highway speeds because a board in the steering wheel fried and shorted your one and only CAN bus.

[@leebarnes655]

I would suggest instead that there are two terminating resistors of 120 ohm each, one in the ecm and the other at the end of the longest stretch of twisted can buss wire device/module what ever that might be. All others in between don't have them or need them such as the defect part causing the waveform misshaping to occur. SCSI hard drives are set up in a similar manner, old school tech, look it up. VW has reduced the utility of the OBDII breakout box as far as can line monitoring goes by splitting it into scanner business only and dieselgatebusiness without a doubt on purpose, on other vehicles I have seen Keith of Staten Island fame, use the termination resistor value to call a defective module and there, it was a 100% good call, all from the OBDII breakout box. On this design I wouldn't be surprised to see a single 60 ohm in the module originating the can lines for the OBDII port due to those can lines being emulated can lines. I doubt they bothered to install two 120 ohms with one at the port.

[@ajpotter4330]

that is correct. From what I've heard they a lot of manufacturers are starting to go back to a gateway module to communicate through for scan tools and other outside devices (satellites). they are going to be setup as a firewall to keep people from hacking into the car. that all being said the gateway module will usually have a completely separate bus with a single 60 ohm resistor. obviously since the only modules on this bus are going to be the scan tool and the gateway module there can't be two 120 ohm resistors. so you actually should check the can bus resistance directly at a module not through the dlc for this reason.

[@teardowndan5364]

In the latter part of the video when he looks at the flowchart, the documentation clearly stated that termination is done at the ECU. At data rates below about 1/100th the wiring length in wavelength, single-ended termination is perfectly acceptable in most cases as signal reflections have plenty of time to die down between bits. On high speed busses like SCSI, and even more so on modern high-speed serial busses where the bit length is shorter than the cable's length, so you need the correct termination at both ends of the chain to prevent reflections from happening in the first place. The bad TCM signal might be interesting to look at with an oscilloscope that has sufficient resolution to catch higher frequency components. If Scanner does that, he needs to keep in mind that he cannot use ridiculously long ground clips for reference as that would act as an antenna and potentially pick up tons of common-mode noise.

[@camwsa]

Love the way the diagnose went, felt like I went back in time to the shop facing the problems, loosing signals, trying to find where to look, freaking diagrams and all.

[@mforrest85]

The resistors are for pulling the can lines back to the bias voltage. And for where the voltage is coming from. It can come from anywhere but I'd take a guess and say the ECM is the one that provides the voltage.

[@ScannerDanner]

I've since learned that each module on a CAN network supplies this same 2.5v bias line. So the answer is ALL of them!

[@pepelapew483]

Very good video i have the exact problem with a 2007 touareg that i purchase from copart ,now i will go and do some mesurement .

[@A.Musa76]

I'm having this same issue on my 2018 Q3 quattro with under 36k miles. Lucky for me it's still under warranty and it's now with Audi (They sent a flatbed to pick it up). The vehicle won't start with the push start. I hooked up my scanner and got the U0101. UPDATE: ECM/ECU is dead. Audi order a new one from Germany.

[@henrymartinrodgers4978]

I know this is an old post. Your differing can bus signals near the end of the video. I would think the signal is buffered with electronics inside the gateway. It will be some sort of isolation transistorised distribution of the can bus. So as if one module goes short, it doesn't pull down the rest of the bus. That's way your not getting the exact same can bus signal on pins 6&14 as you are getting at the TCM.

[@ScannerDanner]

we have since learned more about these systems since this video, thank you for the info!

[@baxrok2.]

Yeah, we used to bust Tom all the time about using 'your' DVM. He does sound a bit like you in the videos as well. Nice collaboration, but I'm still unclear about the terminating resistors on the CAN and modules. I thought the TCM would have a terminating resistor of it's own. I agree with you guys, it would be nice to have a way to verify that the TCM is defective above and beyond how the CAN lines appear. Thanks guys!

[@ScannerDanner]

many different configurations as far as the terminating resistors go is what I am learning

[@wesleymyrick9394]

With putting resistors in the circuit it provides a feedback into the lines so it's it's designed to stop interference that's why the patterns are mirrored you take mirrored patterns and you connect them via resistor they cancel each other out

[@Dasdembo]

I was working with mazdas. It was same. Very difficult to get info on some stuff!

[@rickwilliams9429]

the terminating resistor just kills the signal so you do not have a request hanging out on the can line waiting for a reply or answer from a module. most term resistors on vw family are in the modules, also with vw family you can go in address word 19 (gateway) MVB 125 and up will tell you can communication. If a 1 is read signals are good check power to module, if 0 is read there is a communication issue on the can, which is more than likely a wiring issue

[@jth1699]

Another purpose for the end of line resistor (EOL) is so the computer can monitor the integretary of the wires - if a known voltage is passed through a known resistance then a known current is the result. That current is monertered by the computer - loss of current signals open circuit. Interesting video - it looks like the architecture of the buss is more of a star configuration than a serial configuration and the resistance readings from the transmission read back to the ECU. This type of buss configuration is both faster and safer... Fun video - I just finished up 2 jetta's they were both a pain in the butt.

[@gedion4000]

From my experience, these communication termination resistors keep signals from trying to go back up the way it came. When working with DMX 512, the standard for communicating with moving lights, you daisy chain all the fixtures together. at the end of the line, since there are no more fixtures to connect, that signal wants to try going back home so to speak. a terminator (which is a connector with a resistor bridging two of the pins) is used on the output f the last fixture to prevent any issues with the signal.

[@emiliobolivar7645]

Once the ECM is communicating with the scan tool , pin 7 LED will begin to flash on the CAN Test Box if not the scan tool is not sending the command to communicate.

[@markd6637]

Also you put out great video scannerdanner the audi you were speaking about with a faulty engine mount I've actually seen that a few times it was pretty easy for our shop to diagnose then again we are a Volkswagen shop / Audi

[@cristobalauladell3198]

The voltage comes from all the modules combined. It isn't just one module that makes the voltage. The resistors are there to soak up voltage peaks in the line.

[@motorcyclesandridingfree2899]

The breakout boxes are bad ass I use mine a lot when I have network issues helps me find problems quickly on the network. You could of always cut the Tcm out of the network and checked it's output seperately

[@PandaMan02]

45:00 "that's why!" 41:25 "Thats the datalink going to the gateway, and that's the TCM going to the gateway" i hope you said "you were right" to him

[@renefuller9241]

66.8 is considered good, as the resistors have quite a high tolerance so you will never get an exactly 60 Ohms measurement. My VW Golf has three or more CAN networks. I believe the Powertrain one is the one you need and are on. I agree with you on the VW wiring diagrams, I got an ECU pigtail and the colors and connections are off by a high margin. CAN high is supposed to be pin 79 in the 91-pin connector. CAN Low is supposed to be pin 80 in the 91-pin connector. The Pigtail has one connection on 79 with a different cable color, and no connection on pin 80. I have the original VW wiring diagrams, just like you guys have. If the ODB sniffer is the same as the one I have, one switch is for 12 V always on (30) and 12V Ignition (15). I have the Godiag GT 100+. The K-Line is a one wire network for the different connections in the background going to J533 There is a LIN bus in there too, another one wire network going into J533. There is one for the Radio/Video and such, called MOS I believe. It's a Glasfiber network. On my Golf anyway (2017 Golf Hatchback 1.8L Gasoline powered). The 5V reference circuit is created in the ECU I believe. It has the 5V regulator. But I'm sure you know all that stuff by now.

[@andrewgray3482]

Love it guys. I'm an ex tech and its nice to see you guys sharing this stuff.

[@edwinlomonaco6754]

Several euro manufacturers do comms in a similar way. Proven by Super Mario. One if the things you have to watch out for are gateway modules. If you think of it as a "bus station". Everything goes to it but not always out of it. If you miss the gateway in your diag you'll likely get it wrong. Gateway modules can be tricky also because you'll get codes for other modules having no comms. But it's really that the gateway isn't working correctly.

[@chickennoodle21]

The terminating resistors in the network are there to keep information from "echoing" back into the network

[@rimmersbryggeri]

I think the terminations on this car (VAG) are in the cluster and in the ECM. Couldnt be in the the TCM since that is only present in auto cars. it could also be gateway or BCM but I am pretty sure one of the is in the cluster.

[@Yaaaahaaaaa]

no hay que olvidar apretar los terminales hembra del conector. y como ultimo recurso antes de reemplazar alguna pieza chequear los TBS es decir los boletines tecnicos de servicio. lo digo porque ya me paso. en mi humilde opinion. bendiciones

[@martinrubenstein7943]

Scanner Paul, What a superb video this is! (And I love the background bird song - sounds like there’s an aviary at the garage.). I’ve gone right back to the time I joined SD Premium and I’m catching up on some of the videos I haven’t seen yet. It’s fascinating to see how much you’ve learned about CAN since this video - how much more knowledgeable you now are on CAN.. You’ve answered a few of the questions rattling round in my head eg why do you see a different CAN signal at the DTC as opposed to at the TCM. And all the questions you and Tommy ask each other in this video were going through my head at the same time, so it felt as if I was right there with you. This is an excellent introduction to CAN networks. You should tag/label it as such. It’s also interesting, because I thought you’d see the identical network activity wherever you back-probed or connected (eh pins 6 and 14) - this video shows that’s not the case. (Maybe it is on a certain type of network topology, but this shows you can’t take it for granted.) You’ve never made a bad video yet, Paul, but this one is Pure gold. Looking forwards to watching Part 2 now. You must be really proud to see how one of your students has become a master tech. How about teaming up with Tommy again for another video?

[@unclemarksdiyauto]

Great video. Nice too see some VW stuff. Also nice camera work and multi angles! Will check out his channel too!

[@bwdz75]

The termination resistors are there to absorb the leftover voltage so that it doesn't "echo" back through the wire which has nearly no resistance. Essentially they absorb some of the load to keep the line clean and not staticky. Good question on what generates the voltages, I am not aware of which module does it or if all of them do it.

[@ScannerDanner]

I have since learned that ALL of them do!! That was one of my main questions early on that no-one could seem to answer. Thank you!

[@YouTube.TOM.A]

@ 32.09 Terminator resistors act to kill the package of information when it reaches those terminal limits, I BELIEVE the explanation given to me is that the packages tend to survive the ends of the network and echo through the system with distortion effects. its possible you already had the answer.

[@nukelauncher95]

Another great video Paul. I have a feeling that you didn't realize at that there are multiple CAN busses, and that each bus has a pair of terminating resistors. Each bus is connected to the gateway. the gateway directs signals in-between busses. For example, the fuel pump primes when the car is unlocked by the key fob or the door is opened. The central locking module sends a message saying that the door is open. The gateway sees this message and sends it's own message to engine control module to turn on the low pressure fuel pump to prime the system. if you were backprobing central locking module and the engine control module at the same time as you opened the door, you would see activity on both busses, but it would be different activity. Channel one and two (central locking CAN bus) would NOT look exactly like channel three and four (engine control unit CAN bus.) When you were measuring the resistance of the the CAN bus from the TCM, you are ONLY measuring the resistance of the powertrain bus. you can unplug every single module other than the ECU and your resistance checks at the TCM will NOT be affected. Anyways, you still have some learning to do. We all do. Keep up the great work.

[@LynxStarAuto]

Ian Johnson pretty much spot on. However, the K Bus is the bus which allows communication of the entire network with a scan tool. He was not wrong in chasing a fault in the K line, but his break out box pretty much did it for him. Soon as those LED's shined bright, you have just confirmed integrity of the K line.

[@ScannerDanner]

yes I do, thanks for the info. I was aware of multiple networks on the car, just didn't realize at first about the DLC being isolated from the rest of the CAN network until we saw the diagram.

[@07BSPtC]

Watching this video. Having a similar issue. Multiple failures around communication. Dealer replaces the gateway issues continue. Guessing bad canbus wiring and need to repin a harness or rewire some section of canbus

[@chrismechanic2000]

another great vid mr danner, i think on this car with the gateway, the resistance check at the break out box doesn't tell us much, as you said on other cars without the gateway it woulld be a valid test.

[@fdseoulsandiego6514]

Awesome vid as usual Paul. I hate not having a definitive reference data base(picture.# value.) on what is a good/bad BCM to be 100% sure if the component needs changing.

[@carlosalfaro9467]

dude you should work on toyotas and nissans it will be so helpful for us here , i am from COSTA RICA we dont get many american cars here do to fuel ecomony , your videos are excelent you are a very good teacher . compare to all other videos ive watch, you are the best. only thing is here in COSTA RICA we learn and go by ear lol since we dont have the tech equipment you have snap on... here super expensive we dont get pay much here like for example if i was to replace a cluth on a toyota 4x4 ill only make like 150 dollars labor compare to USA, MAKES A BIG DIFFERENCE , so we go as we can , learn and trouble shoot and handle it as we can with no sophisticated tools lol okay i just wanted to say thumbs up keep the good work

[@chungaleta1234]

Another Tico here. You are correct. I'm one of the few who own an American car and I have to work with what we have. Problem here is,, modern cars with intricate systems and no equipment to diagnose and repair. I haven't seen one Snap on scan tool or smoke machine in any shop around here. Pura Vida!!

[@carlosalfaro9467]

TRUE . THAT PURA VIDA PEACE.OUT

[@vincebauer4777]

great video danner...i just got my otc box today u just answered a ton of questions I had wow thank u

[@shawhartline1266]

I was told the resistors in a can network act as "echo" reducers for a clearer signal. Think sound deadening walls in a music studio. I'm not sure that's the main reason but just what I heard.

[@theheavymechanic4949]

You should try a bidirectional test with the tcm unplugged with a trigger on the diag socket traces. maybe they will be an exact match as the gateway should send the command you are sending to the ecm?

[@kdmq]

I almost feel like the 60 ohm measurement you made on pins 6 and 14 were measuring a resistor in the gateway module and one in the scan tool. If you unplugged the scan tool during that test it would be cool to see if the measurement stays at 60 ohm or goes up to 120 ohm. If it went up to 120, this would prove that the test of pins 6 and 14 was _invalid_ for checking the main CAN network of the car itself. If there was no change, then you could unplug the ECM and see if the resistance goes up to 120 ohm. If it does, this would prove that the test of pins 6 and 14 was _valid_ for checking the main CAN network of the car itself.

[@richardmcwhirter9396]

Brilliant work!best video yet thanks

[@pedrolriveranegron5178]

Hi my good friends Paul and Tommy.... bleesings!Another great use of the "Breakout box" is that you can use it to make (current) compression tests.Just connect the "Breakout Box" to the obd port, then connect the Verus in oscilloscope mode to the breakout box (+ side and -ground) Then, use the function "AC-COUPLING"

[@michaelfrancis3261]

Awesome!! I think this would help so much for what I'm working on right, love that new tool that reads the data link

[@jhauna1]

It really depends on where the resistor locates, that will determine your resistive result.

[@weldingjunkie]

Bannie Thompson say what?

[@offtwoaces]

If you want more info on CAN Bus design, try doing a google search for CAN Transceiver Application Notes. You will find detailed information from the integrated circuit companies which provide the chips which are used in the modules along with the theory behind the bus design. Perhaps too much detail ;-).

[@asavage1576]

I love datalink and emissions troubleshootingn

[@gloriawoods2313]

Thanks guys

[@5Dale65]

You mentioned the K and L lines. Older VW vehicles, like pre 2004, you can diagnose only by talking at the K (pin 7) and L (pin 15) lines. Those veh-s didn't have the CAN stuff implemented yet. And those were really simple and easy to connect to, you could just use an 'amateur' OBDII-to-USB (or RS232) cable for $10 and a laptop. Those cables are named 'VAG KKL', here in Poland you can buy them almost everywhere.

[@frankl1955]

Is that why I never see signal activity on pins 6 & 14 on my 2003 toyota and my 2004 kia? And only on 7 & 15

[@seychelles44]

i think you'll find the number prefix for ecm central electronics etc will be the binary code for that componant

[@throttlebottle5906]

termination resistors should be at the two furthest end devices/harness locations. there could be multiple can buses

[@Sam-lw6mx]

the engine ABS transmission ECUs are linked through the high speed CAN network. you can have more than one high sped CAN networks. e.g. used for the smart engine actuators.

[@anks888]

Looks to me that the can bus isn't terminated correctly at the TCM probably bad resistors or transceiver in the TCM. If you can get inside the TCM you maybe able to repair it. Also you can check the resistance of the pins at the actual TCM unplugged.This would show if the module is loading the can lines down.

[@ScannerDanner]

Thanks for the information Kris!