Passat 8/98 AFN - CAN-Bus am MSG vorhanden oder nicht? | Posts 32+

Jochen_145: Do you happen to know what that component is exactly, located at the output of the control unit? I suspect it's some kind of throttle...

So, the missing components are basically the CAN-CPU, bus driver, and the component at the output... I haven't been able to identify them precisely yet.




Hello, I need to take another look at that; I'm not entirely familiar with MSG either.

You actually only need the transceiver. It's an integrated component with a bus clock and bus driver.
The terminating resistor for VAG control units is located within the device itself. Therefore, you would need to solder a 60-ohm resistor between CAN high and CAN low (since it's a star-shaped network).
I think that's probably the 'choke' you're referring to.

I will, however, double-check the information and get back to you if I'm not remembering correctly right now .

Best regards, Jochen.

Hi,

Okay, and then what? What's the point of replacing the hardware if the software can't work with it?
This topic is starting to hurt a little.

Best regards, Rainer.

Rainer, you might be wrong here - someone else actually had success with a similar story in another forum (using an engine control unit that was even a bit older than mine) - but in that case, it wasn't done by replacing parts with new ones, but by 'transplanting' components from a much newer ECU - without any software changes! I personally don't mind experimenting - and if I can get a CAN-Bus retrofitted for 15 euros (that's about what the whole thing costs at Reichelt), why not? Learning by doing - if it works, great - if not, it's 15 euros down the drain - and it gives me the chance to install newer software on the MSG. The fact that the software can be recoded to 'automatic' (and thus CAN, which we've already talked about) suggests that something might be possible (the ECU doesn't allow any other coding changes besides those two bits, 0 and 1, in the coding).

Jochen_145: To be precise, the Intel CPU (82527) and the bus controller (PCS82C250) are missing, as well as the part mentioned above (I'm quoting from the email correspondence: 'B82793 underneath S513 N underneath 0375 from the company EPCOS' - perhaps someone will come forward with more information... I haven't found anything yet).

[EDIT]Found on the EPCOS website... however, no source of supply has been found yet.[/EDIT]

Hi!

So:

I just disassembled half of my car! I can't find the CAN bus wires anywhere!

There aren't any in the control unit either!

There are 3 lines connecting the MSG (Manual Selective Gearbox) to the automatic transmission.

Purple/Black.

Yellow/Black.

Brown/Yellow.


I'm measuring 2.54 kHz on the black wires! One has 10.54 volts, and the other has 2.54 volts!

The brown/yellow wire also has 10.54 volts and a frequency of approximately 0.45 kHz +/- 0.5 kHz.

Then I tried connecting the CAN bus from the instrument cluster there, but there was no reaction!

The CAN lines operate at 2.54 volts! Then I tapped into the comfort CAN, but there was no reaction!

Do your AFN engine control units have 2 connectors? And I have a request!

Wo sind die CAN leitungen bei euch angeschlossen? At the MSG!

Thanks and best regards,
Olli

I'm measuring 2.54 kHz on the black wires! One has 10.54 volts, and the other has 2.54 volts!

The brown/yellow wire also has 10.54 volts and a frequency of approximately 0.45 kHz +/- 0.5 kHz.



Hello.

I believe the two black cables are twisted together.
Based on the measured levels, it is clearly a low-speed CAN bus used in passenger vehicles.
On the MSG, it's CAN High-Speed.
This is located at terminal T 121/7 for CAN High and T121/6 for CAN Low. My control unit has two connectors for the T121.

Specifying the frequency for the CAN doesn't help me. Please measure the time for one period, and then you can determine the baud rate. I think it will probably be 100 kbps.

'This will prevent communication from working, as different CAN buses are being connected.'

Best regards, Jochen.

'Two connectors... The wires are marked as Orange/Black (Can-H) and Orange/Brown (Can-L), corresponding to pins 68 and 75. Unfortunately, I don't have much time to work on this right now... But I will continue to look into it.'