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in this thread: http://www.passatworld.com/forums/42-volkswagen-passat-b5-discussion/358037-using-oscilloscope-can-bus-door-locked-solid.html the OP stated he was trying to read some data off the CAN Bus in his car, a 98 B5 in the UK.

I replied probably in a rude fashion (as I am wont to do on occassion - tact and diplomacy are not always my strongest suit in a textual format like this one) and told him and a couple of other folks that there was no CAN Bus on B5 models - to which they replied BS and cited "sources" supporting their claims (a Haynes manual is *not* a good source, guys - a Haynes manual on our cars has more bad data than good), and I argued back, and then got shouted down by a couple more people. another source cited was Ross-Tech's website - now that's a source I can dig into, cuz Uwe Ross knows his stuff.

I know I'm old, and my brain might be reminicent of swiss cheese upon dissection, so my memory might be suspect at times; so, I did some digging. here's what I found...

clearing up CAN vs non-CAN Bus.
CAN stands for controller area network. the bus is the vehicle bus that allows for exchange of info via microcontrollers without one centralized controlling station. the data rate is as high as 1 MB/sec, and that's loads of info in near real time for a car. for the implementation VW uses, they throttle the data to what appears to be half that rate (500KB/sec).

Ross-Tech does not say all of our cars have CAN Bus. from this link on their site, it states that B6 and newer models have it, and not older ones.

I wasn't totally satisfied with that answer, since I asserted earlier that B5.5 models had CAN, but not B5s; therefore, I did a little more digging on their site. having been here for as long as I have, and remembering how many folks had a problem with after-market radios and having K wires put at +12 volts due to the new radio (and dealers saying their cars couldn't be scanned because of it) reminded me of it. the K wire was/is used for ODB-II diagnostic reads using the ISO-9141 interface requirements on B5 models, and the data rate was/is 10.4KB/sec - much slower than the CAN Bus.

the newest CAN Bus international standard is ISO-11898, the older CAN Bus is ISO-15765, vice the previous ODB-II interface (ISO-9141) using just the K wire. VW used the same connector specified by international standards to implement ODB-II physical interfaces for a reader.

from this page on Ross-Tech's site, info is provided regarding the K wire (but not much). the important take-away is that aat some point during the B5 production years, VW decided to include radio diagnostic data into the data OBD-II colleected, and ran the K wire to the radio; after-market radio installations shorted the K wire to +12 volts, rendering it impossible to get any diagnostic data off the ECU, etc.

at the bottom of the previously linked page in my previous paragraph above, it discusses the instantiation of CAN Bus into radio diagnostics and shows the connectors for CANBus for B5.5 models. the only thing I know of on the B5.5 models that uses CAN Bus is the radio, but I might be wrong there. the easiest way to tell is to hang an o-scope off the K wire on a B5.5 and see if there is data on it while pulling codes...

Lastly, discussions of K wire-based OBD-II diagnostics can be read about here: On-board diagnostics - Wikipedia, the free encyclopedia and scroll down to "OBD-II diagnostic connector" to see the pin-outs (yes, the ODB-II connector also has CAN Bus pinouts dedicated to it, but B5 models did not use it then, only the K wire) and again on the previously linked page on Ross-Tech's site, Ross-Tech: VCDS: Afterrmarket Radio Problem - it's pretty clear to me that all vehicle disgnostics went thru the K wire and not from a CAN Bus, as it did not exist in Passats then.

to wit: ISO 9141-2: This protocol has an asynchronous serial data rate of 10.4 kBaud. (Jay's note - baud = bits/second) It is somewhat similar to RS-232; however, the signal levels are different, and communications happens on a single, bidirectional line without additional handshake signals. ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles.
  • pin 7: K-line
  • pin 15: L-line (optional)
  • UART signaling
  • K-line idles high, with a 510 ohm resistor to V[SUB]batt[/SUB]
  • The active/dominant state is driven low with an open-collector driver.
  • Message length is restricted to 12 bytes, including CRC
for the older members here, the VAG-COM cables we used to use were RS-232 cables that plugged into the RS-232 port on our old Windows-based PCs on one end, and the ODB-II port on the other. yes, I've used that cable. data rates on RS-232 would not support CAN Bus, whereas the K wire implementation for ISO-9141 data rates specs are great for RS-232 data rates!

with the OP stating his UK Passat being a 98, I think it is clear he has a B5. I also think it safe to again say that it does not have CAN Bus.


if you guys want to discuss this further, please do. I'm satisfied I wasn't talking out of my arse, but I'm willing to listen - I've apologized for overloading my hummingbird ass with my alligator mouth before here...

I'm making it a sticky so it is more easily seen and doesn't get lost in the day-to-day noise of the site.
 

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Technically, the B5 actually does have a slower version of CANBus, but it's only used to pass communications between the CCM and the electronics module in each door. As you've already mentioned, it is not used for OBD-II.
 

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believe the b5.5s have the k wire which in essence is an early version of can bus but less complicated with its interpretation hence why on my b5.5s I have had I have had no problem replacing stereos with aftermarket units without any adapters all you have to do with them and swap the power leads over with the Passat having the permanan t live on the ignition live cable but I bet what makes people believe their cars have can bus is vcds calls it a can bus system when its k wires
 

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Noobie here - first real post. I have a 1998 B5 VR6 that is running rough above idle but only as speed increases. I understand that an OBD-II reader may be able to identify the problem for me. Being frugal (or cheap, I'm not sure which) I found this inexpensive reader: Autel AL301 OBDII Over The Counter DIY CAN Code Reader
at JB Tool Sales and I wondered if it would do the job. If so, where do I plug it in? (I am new here and the car is new to me. I found the fold-out cup holders, the trunk button and the gas cover button so far but the hood cable apparently is non-existent - just to know, what do grills cost?) As with any noobie, any help at all with this problem is definitely greatly appreciated.
 

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I would advise against a generic code reader they cant read half the stuff on the passats my suggestion is a imitation kkl lead off ebay with your computer via vcds lite and it might be in the drivers footwell under the steering wheel that's where mine is in front of the pedals hope it helps but might be too late
 

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In my experience the newer b5 (late '99 and 2000) do have can bus here in Europe, although the only things that use CAN on those models are:
Automatic Gearbox Computer
CCM
Instrument Cluster (Which also contains the CAN gateway in the B5, in order to use it for diagnosis)
ECU
And maybe, but I don't know for sure, the Fuel Pomp Control Module

My V6 TDI also has CAN and it's from march '99, so that's where I think VW in Europe started to implement it in the Passat. Correct me if I'm wrong.
In my car it's not for diagnosis but for communication between the Automatic Gearbox Computer and ECU. And for the door modules and the CCM.
I'm missing the CAN gateway in my instrument cluster, but the wires are there, even in the ODB-II connector.

So, resuming, there might be a slight difference between the European and American version, but here in Europe, the B5 late models do have CAN and the B5.5 models also have CAN.
 

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Sorry to revive an old discussion but I'm trying to fit a 920 instrument cluster from a late '99 B5 into my '98 B5 that has a 919 cluster. While I've managed to determine that almost 90% of the pins are the same, I'm not able to figure out how to get the tachometer to work.

On the 919 cluster, pin 11 on the blue connector provides a signal to the tachometer. However on the 920 cluster, pin 11 on the connector is unassigned. Not sure if the cluster itself can still accept the legacy signal from pin 11 of the '98's blue connector to drive the tachometer.

Also come to understand that the 920 cluster from late '99 have an earlier implementation of the CAN gateway incorporated into it. Many people have told me that the tachometer on these clusters gets its reading through the CAN bus. Indeed, when I checked the wiring harness of the donor cluster and mine, I found that pins 19 and 20 have been assigned as CAN high input and CAN low input respectively, while pins 27 and 28 have been assigned as CAN high output and CAN low output respectively.

As late '99 Passats had drive-by-wire throttles and an ECU based on BOSCH ME7.5 while earlier models had drive-by-cable throttles and BOSCH ME3.x ECU's, I'm wondering where the 920 cluster's CAN gateway taps the tacho signal from. As it is right now, this is the ONLY thing I've not figured out as yet and I'm wondering if anyone has had the experience of getting a 920 tacho to run on a 919 harness.
 

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The AHA & AEB used a similar ECU with different programming.
I believe the Auto AHA had a CAN-Bus connected from the ECU (T80/41 High T80/29 Low) to the ATM.

You might be able to connect there (using twisted pair cable), but it might not be a compatible Bus, and probably doesn't supply the required data. If it is not an AHA with Auto Trans. it might not have the CAN-Bus programming in the ECU.

This could damage the ECU and/or Cluster, use of this information is at your risk.

I don't of any verified way of connecting it.
 

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I don't know a lot about pre late 1999, but I think most if not all B5s with remote central locking would have had the CCM CAN-Bus,
and the Power Train CAN-Bus was phased in toward the end of this period.


I believe the following is correct from late 1999 to the end of the B5.5 production.
The Power Train CAN-Bus in the B5 & B5.5 actually connects to the ECU, ATM, ABS, Instruments, and CAN Gateway.
There is separate CAN-Bus which provides communication between the CCM, and the Door Control Modules. This system was upgraded in the B5.5 with a faster CAN-Bus.

The CCM CAN-Bus does not connect to the OBDII Port.
The Power Train CAN-Bus does not connect to the OBDII Port, unless a Tachograph is installed.

The K-Line is a separate communication system for diagnostics and is connected to the OBDII Port.
 

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b5.5 atq 2.8 fwd. i have an ELM237 Bluetooth odb2 port scanner, I use Torque app to read clear codes and check real-time info, when the key is in on it works, but as soon as the engine fires up, it drops the communication with the app, and says channel busy, so no real-time info in the app, I have tried odb2 car doctor pro and gives me real-time data, but it is a hit and miss by the way I have P0170 and p0173 fuel trim bank, i´m still googling that, but a hint won´t hurt.
 

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Bringing up this topic again...

I spoke with a former roommate of mine who has been playing around with CAN enabled micro-controllers and programs. It is relatively simple to understand if you have a basic understanding of programming and coding. CAN-bus enabled vehicles have modules that all operate on the same data transmission line. In other words, every module is connected to each other and can be communicated to on the same line. When an operation is requested, coding is transmitted on the line to every module. The module interprets the coding and will only execute a task IF the first part of the coding is registered as a "start" function. If not, the module ignores the signal. I believe the K-line is just a slower implementation of CAN-bus.

A CAN-Gateway, which was implemented on later Passats, enables a "translator" between all of the modules of the car. This means that instead of sending the signal to every module, the gateway interprets the signal and only directs it to the requested module. For example, if I press the window down button for the driver's side front door, the gateway receives the signal, and interprets it to only be that door, and sends the signal to only that window controller. Older versions of CAN-bus would have sent that signal to every module in the car, leaving the module responsible for interpreting the signal. The idea of the gateway is to make installing additional modules simple, as you only enable a feature of the gateway instead of introducing new coding for all the modules to have to interpret.

This would explain why when the ABS controller fails in earlier cars, the diagnostic line becomes corrupted and can make other modules unreadable.
 
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