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

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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 youtu.be/GPQ8EKtvM_g we repair this vehicle and are surprised by what we find.

Here is the link to Tommy’s YouTube channel
Positive Lead Diagnostics www.youtube.com/channel/UCiFSILHjs5XZecZJDwn7ieA

Tools used
– Test Drive Test Leads for the Snap-on VERUS
– VCDS® with HEX-NET® Pro

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– Poor running, flashing CEL, no codes (bad computer ground) – Toyota
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– ScannerDanner Premium Audi S5 series

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.
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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!


5Dale65 says:

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.

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ChayD says:

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

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feargal mulvany says:

@scanner danner The resistors are there to reduce line bounce or network noise

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James Lee Jr says:

hey scannerdanner I have an question. my question is. I have an 01 Ford experdition 4.6 liter engine. it has a miss in the engine under load. I changed the sparkplugs, test fuel pressure. on fuel test I got 30psi engine off and 40 psi with me power brakeing it and pressing the gas. I feel like an ign coil. but I cant afford to replace them all. but I don't have spec for ohms reading of the coil sec or primary side. but with miss being on sec side should be something dealing with sec side of ign. like spark plug maybe compression or the coil. im I correct. maybe next step is to pull the coil under load why it missing or ohm it out? thanks for help. this is my personal vehicle

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Petar says:

15:30 the guy said "green crusties".Same as Eric O. 😀

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Rick Hayward says:

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

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Twin Keys says:

If you have 2 terminating resistors at 60 ohms each and you unplug a module, how do you still get 60 ohms? I heard where one of the resistors was in the ECM, where is the other?

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Vince Bauer says:

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

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Caveman4860 says:

Thank You!!!

Yep,.. it's a Long Video…! As also an ASE Master w/L-1, This type of "lack of Correct (if Any) Information",.. is Common! I use a 4 ch. MODIS (old one, No USB) Just for my Scope applications.
My Boss/Owner thinks "Here's the Code, Why is it Taking So Long, to Fix it?.."
(he hasn't kept-up, with What these Comm Issue's are Like!!)…

I took a Pic of the 4-line Comm Signal (on my C#), to Show and 'help explain' This type of Issue. And Why… it can be Misleading!! [not infringing on any Copyright issue's.. I Hope]

Again,.. Thank You! For Both of Your Time, to make this video!


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MiracleMAX says:

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/YouTube 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 YouTube creator for almost 2. (Sorry for the plug….)
Great to see you guys working together.
Keep up the good work!!

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Andrew Gray says:

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

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geo dude says:

Humble Mechanic VS Positive Lead Diagnostics !!!

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geo dude says:

does your book explain how to test modules? ive been back and fourth on purchasing your book. as money is a bit tight lol . but dude scanner danner your the man !!!! i know it will be money well spent

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auto uk says:

u both best

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Mike One says:

love how you guys kept it real

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Mike One says:

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

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R230Tuner says:

Also you cant set a trigger on a Bus (CAN) signal as it is always changing and not a repetitive signal. You need to turn the trigger off to see the signal as it comes through the data bus, and watch it live or review it from the cached data stored in the scope (playback).

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R230Tuner says:

A gateway is a union between two or more different networks using different protocols. That is why you dont see the same data at the DLC as you do on the CAN lines at the TCM. The gateway translates data between networks like your gateway at home on your PC network translates data between PC's and other devices and the phone line which it connects to (internet). It's akin to translating one spoken language into another different language meaning the same thing. In the end it's cost savings for the manufacturer. If there is no need for high sped data communications for a module to another, they use a lower speed data bus (line) and use lower speed data bus components which are cheaper to accomplish the same outcome. In some cases it is also redunduncy in case one communication line goes down, the crucial modules can still talk to one another.

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Morgan Reyman says:

open the tcm and check for corrosion

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Michaela Myers says:

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

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Glen O'Hara says:

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.

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Paweł Czechowski says:

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.

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Ryans Automotive says:

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

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richard cranium says:

im thinkin that gateway is a cheap way of making the european setup work with usa standards. call it the fricken ze translaterin module. so much easier to do than change the whole system and more cost effective. chances are the same car in europe has everything the same but this.

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Valentin Aja says:

you guys are great

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sam allen says:

i subd too tommys channel awhile back I had the feeling they were SD disciples good stuff guys all that studying of canbus I did came In handy I went deeper than needed as far as canbus goes the hexadecimal language and so on just stuff an engineer might need not a auto tech

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gst69man says:

not a good move to go to premium.
I am for vids for free. free as you get money from views. Your subscriptions will rise also. those who do not charge, like chris fix, get much higher views and subscriptions, and thusly more money. just saying.

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Paul Lenzen says:

"warum machen ist einfach, wenn kompliziert funktioniert genauso gut"

"Why make is simple when complicated will work just as well,"

It's the German way.

Would have been interested to know if Tommy was able to speak with the customer directly and ask just what went on prior to the no shift problem. " Yeah, I had a problem with "XYZ" and a buddy and I tried to fix it and checking the fuses" or something like that.

Only reason I mention this is I got caught on problem with a buddies daughters car. She went to the Quickie Mart for something and came out and her car would not start. Crank but no start. No spark, but had fuel. I messed with that thing for couple hours and she stopped by and I was speaking to her about it and said that she needed her wallet from the consul that she put in when she came out from the store. Said that everything was fine until she put her bill fold in there.
Dug all the crap out of the consul and found that previous owner had put and anti theft toggle type switch that cut off power to the IGN. When she put her wallet in there it tripped the switch. Grrrrr

I realize the service writers in Dealerships are a "Buffer" for the techs, and very few service writers are techs. They just write up the service order as quick as they can because there are 5 or 6 people standing in line.
But in this case, where it was particularly tricky and potentially particularly expensive, maybe 10 minutes on the phone with the owner 1 on 1 may have led Tom to the fuse box.
maybe………… maybe not. Nice find though.
2 thumbs up.

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