Passat AFN: CAN-Bus on MSG - Yes or No?

Hi,

Unfortunately, despite really searching and reading (which I always advocate!), I haven't found any reliable information about whether the MSG (Modular System Gateway) in my Passat 3B uses CAN (Controller Area Network) or not.

Year of manufacture: 08/1998, engine code: AFN, ABS factory-installed (no ASR/ESP).

In the wiring diagrams for the MSG (Modular Service Gateway), the CAN bus is only documented starting from 5/99 – and the diagrams I have also do not show any ABS (Anti-lock Braking System) wiring.

Does anyone have an idea or reliable information, before I decide to go to the workshop with the oscilloscope this weekend?


Best regards,
Marcus.

No, that one doesn't have CAN. CAN technology wasn't introduced in the mid-range models of Audi/VW until the middle/end of 1999.
Also, why would the wiring diagram for the engine control unit (ECU) include the ABS wiring? They are independent systems.

The '5/99' refers to the availability of the CAN bus on the instrument cluster, which is correct. That's exactly what I'm doing (replacing the old 919 instrument cluster with a CAN-enabled one), and before everyone starts shouting 'it's not possible,' it *is* possible, as long as the main system control (MSG) has a CAN interface.


I have already read the discussion about ABS/MSG communication, but unfortunately, the discussion about CAN/K-lines for ABS seems to have stalled: https://community.dieselschrauber.org/en/viewtopic.php?t=12287

Unfortunately, there wasn't a real consensus.

'The AFN used to exist for a longer period, so here are some questions beforehand:'
1) Which MSG would be suitable in this case?
2) Would this fit in a direct exchange?

That's actually exactly my problem.

I would also like to use the CAN bus from the MSG.
My current ASV score (which should be the same as the AHF score):
CAN is not active at the switch! (I have already verified this.)
The CAN (presumably referring to a specific feature or system) is only active with automatic transmissions or ESP (Electronic Stability Program).
Re-programming my engine control unit (ECU) to automatic transmission is not possible with my current level of knowledge.
I am currently trying to determine to what extent a tuner can activate the CAN bus when performing engine tuning.

The communication protocol for ASV/AHF to AI is K-Line, regardless of whether it's an automatic system or an ESP.
The gateway is present in the AI system, but it is not used for display purposes.

An automatic message-sending gateway (MSG) has an active CAN (Controller Area Network) interface.


Best regards, Jochen.

Interesting. I took some time this weekend and wanted to 'just for fun' connect the two necessary pins and take some measurements - I opened up the connector and what did my tired eyes see? Two orange CAN bus wires were connected to exactly the pins that would be relevant.

I was already looking forward to it and had the oscilloscope connected, but unfortunately, it didn't work... there was no signal coming from the wires.

The theory involving automation isn't bad in itself. It would explain why the wiring is already in place here...

I've also considered the possibility of reprogramming the control unit to enable features like automatic transmission or anti-slip control, or something similar.

My MSG should be able to be recoded to automatic (according to the diesel mechanic) - maybe that will get us a step further. Thanks for the feedback and the idea - maybe things will work out with the WFS3-KI in my old 3B after all.

No, it doesn't have CAN. CAN only came to the mid-range models of AUDI/VW in the middle/end of 1999.

I had a motor control unit from 03/99 in my hands that has CAN communication. (TDI) It is probably intended for the ASR (Anti-Slip Regulation). This signal is suitable for speedometer modification.

Does anyone happen to have wiring diagrams for a 3B (AFN) engine with an automatic transmission?

What would be the point of having automatic vehicles with an active CAN bus connected to the MSG (Modular Service Gateway) if they weren't actually using it?

What would be the point of wiring the CAN-BUS to the cable harness at the MSG (Modular Service Unit) more than half a year before its official launch, especially when cost-cutting measures are being implemented everywhere else?

I'm currently trying to figure out how/whether the automatic transmission control unit and the main system gateway (MSG) communicate. Jochen has already made some progress on this, as you can see in other threads. The question I have, and the reason I'm looking for the wiring diagrams, is: do the MSG and the automatic transmission control unit communicate with each other, and if so, possibly via CAN?

Admittedly, that's just grasping at straws...

Hello,
The automatic transmission, which has a Tiptronic function, is connected to the engine control unit via CAN (Controller Area Network).
However, at this point, CAN is not always being discussed.
It was also only used to connect the automatic system with the MSG and ABS.

This transmission was already used in the Audi A4 (B5), which already had CAN bus technology. Therefore, because the vehicles are modular, the wiring was already in place.
Even something like that is a form of cost reduction.
By the way, the Passat '97 also had a ComfortCAN system if it was equipped with a remotely controlled central locking system.
At this point, the benefits of CAN depend on the specific equipment being used.
It wasn't until the model year 2000 that it was fundamentally introduced.

What is the purpose of having a CAN (Controller Area Network) interface on a switch in an automated system?
Simply put:
This combination instrument, of a more modern design, reads all the information from the CAN bus. It doesn't matter if it's a manual or automatic transmission, or anything else. It works as long as the desired IDs are present, even if it's not originally intended for that vehicle.
Wa hierbei noch zuklären wäre: was macht das MSG wenn nichts vom Automaten kommt ? Nrunoff ???

Best regards, Jochen.

I'll try it out tomorrow or on Sunday, depending on how much time I have.

The Passat '97 also already had a KomfortCAN system, if it was equipped with a remotely controlled central locking system.
At this point, the benefits of CAN depend on the specific equipment being used.
It wasn't until the model year 2000 that it was fundamentally introduced.

Every Passat (from model 3B onwards) has a comfort control unit, regardless of whether it has a folding rear seat or not. And all models from 3B onwards have the comfort CAN bus. The door control units are connected via this. Only the level of connectivity and the speed of communication changed over the course of the model's development.

Yes, all 3b models have comfort features.
If your information is correct, then I could potentially trade my station wagon for a 3bg model because, theoretically, I would need to install a CAN bus system.
How can that be verified? Specifically, the communication to the AI, MSG, and Tiptronic control units is working without CAN. My VagCom interface can't do that.

x world one: That's exactly the goal, yes (darn, I've been caught ) - a 920 847 in the old 3B. In principle, that should indeed be possible - Schorni in the 3B forum has already done something similar, although he replaced the MSG (as part of an engine swap). In principle, it should then be enough to connect the two CAN lines from the MSG to the instrument cluster - and it would even have all the functions of the comfort CAN (door open, etc.) in the instrument cluster.

It's essentially only possible to check if CAN communication is present using measurement equipment (oscilloscope or CAN analyzer). Whether enabling it will allow the MSG (Module Software Generator) to be reconfigured for CAN communication (without any side effects) is something I need to check on Sunday.

'Changes to the CAN bus speed should not be a problem, as the transceiver initially sends several synchronization bits, allowing listening devices to adjust to the speed of the subsequent data word. It is perfectly possible to operate different speeds on a CAN bus (another common misconception is that comfort CAN buses are incompatible with each other due to different speeds).'

x world one:
Incidentally, a changed CAN speed should not be a problem, as the transceiver initially sends some synchronization bits so that listening devices can adjust to the speed of the following data word - different speeds can easily be used on a CAN bus (another rumor suggests that comfort CANs are incompatible with each other due to different speeds).

Stop! Stop! Stop!!

Please don't confuse these things, or you'll mess up the CAN bus!
The synchronization bits are determined by synchronizing the transceivers within the defined tolerances. This involves only a few kilobits.
Fundamentally, the baud rate must be correct; otherwise, you'll get error frames and potentially damage the CAN bus.
In the new VAG models, the ComfortCAN operates at 100 kBd, while the Powertrain CAN operates at 500 kBd.
The baud rate must be the same for all participants. However, each clock has tolerances, so one device might transmit at 499 kbps while another transmits at 501 kbps. You can synchronize this to some extent, but no further.

Furthermore, the Comfort-CAN is a low-speed automotive CAN bus with a 12-volt voltage level. The Drive-CAN is a high-speed automotive CAN bus with a 5-volt voltage level (which applies to the CAN High line). This also generates garbage data!
Now I know that the Audi B6, and therefore the Passat, has some kind of problem on the comfort CAN bus. I haven't measured exactly what the issue is yet.
It's possible that these devices also use the Kofort-CAN interface, but with a high-speed configuration but a lower baud rate. I'm not sure about that.
What I'm certain of is that these models deviate from the essentially homogeneous CAN environment of the Volkswagen Group.

So, be careful about connecting them together, that definitely won't work (not to mention potential CAN bus conflicts).

Try measuring the Comfort-CAN line with a voltmeter against ground (GND).
If the measured voltages are the same here, you can at least be sure that you have the same CAN type.

Best regards, Jochen.

Oh, darn. I'm quite happy with my 3B Kombi overall, except for the defective FIS (the display becomes blurry at temperatures above 20°C).
"I would just like a door-open indicator."


Unfortunately, I don't have an oscilloscope, otherwise I could have measured it. If you need any information that I can read out from my automatic transmission using VAGCom, just let me know.