CAN Transceiver for ASV MSG Systems

Hello everyone,

I haven't made any progress yet in activating the CAN bus on my Seat Leon with a TDI engine and ASV motor.
Following a phone call with a tuner, the question now arises as to whether the CAN bus hardware is actually present.
I tried to measure the pull-up resistor. Since it's not measurable, it's possible that the transceiver on the circuit board is not present.

My question is:
Has anyone ever checked if the CAN module is present on the MSG when soldering in new chips?
Are there different software versions for the steering control unit (SCU) from ASV, depending on whether the vehicle has automatic transmission or ESP? Or do the software versions actually differ only in the software itself?

Perhaps someone has both control units in stock and can take a look. By the way, my control unit has version 3357.

Thank you for your help.

Best regards, Jochen.

Hi Jochen,
The CAN transceiver needs to be populated.
The termination resistor has nothing to do with the transceiver; it's only connected to the...
equipped at both ends of the bus - so it depends on the topology of the specific bus.
If the MSTG is not a termination point, it also does not have a termination resistor.

Best regards,
Rudi

Hello Rudi,

Thank you in advance for your answer.
In the PQ 34 platform, the CAN bus for the drive system is arranged in a star configuration.
Therefore, in the presence of the terminating resistor, a resistance of approximately 60 ohms should be measurable between CAN-High and CAN-Low.
If I'm correctly informed, the star point is located in the MSG.
This resistor can be equipped with a switchable configuration. However, the problem is that I can never measure it when it's in that configuration, because it's either switched off or its signal is superimposed by the CAN power supply.
For this reason, I assume that it must be permanently installed when the transceiver is fitted (otherwise, diagnostics would not be possible). However, I am happy to be proven wrong.

Do you know if I can activate the CAN bus using the corresponding MSG software?

Best regards, Jochen.

Hello Jochen,
As far as I know, there's nothing star-shaped there (perhaps with the exception of the mechanical cable routing).
The problem with the corporate-level CAN bus is that the bus is no longer terminated at just the two ends.
but that all participants, except for the MSTG, have a 2k6 connection. The MSTG has a 60 Ohm connection.
'In some cases, these resistances cannot be measured because they only 'occur' when the control unit is powered.'
(They are not actively switched on, but are simply present - for AC signals).

I haven't had to deal with the post-activation of the CAN interface until now.
I can't think of any other applications besides speedometer customization...

Best regards,
Rudi

Hello Rudi,

You are absolutely right with your description of the termination resistors.
This is typically done when the CAN network is configured in a star topology.
On the other hand, as you said, you connect two 120-ohm resistors to the ends of the network. All other components do not need to be terminated.
With the unique 60-ohm resistor in the MSG, you essentially have the star point.

The reason for the delayed activation of the CAN is very simple:
I want to log the car's operating conditions in order to see and classify things like temperatures and load profiles.
The vehicle is being used for testing measurement technology. The CAN bus is a suitable data source for this purpose, as otherwise I would have to duplicate every relevant measurement value.

I don't think anyone else is interested in this topic, but I thought that maybe someone might have experimented with CAN before and have some relevant experience.

Too bad, but thank you for your effort.

Best regards, Jochen.