Reading data from a car using Arduino and MCP2515

Hello, I have a question. I want to read all the CAN values from my car using my Arduino. I bought an MCP2515 module for this, and the connection to the module is working, but I'm not getting any CAN values. Maybe someone can help me .

Hey Ak2113,
Where did you go to get the CAN bus system?
You won't find a standard CAN bus at the OBD port; you need to use diagnostic requests instead.
I went directly to the CAN buses, which are located on the front of the connector panels. However, you'll need wiring diagrams for the vehicle.
Once you receive those IDs, you won't be able to do much with them either, as they only contain raw data. It took me 4 years to get about 50% of the data that was actually useful.

Best regards, Ulli.

Okay Thank you in advance and how do I request the diagnostic CAN data ?

Ak2113 wrote:

...to read data from my car...

Which one? As the previous poster already wrote, depending on the model, absolutely nothing happens on the diagnostic CAN bus by itself.

Best regards, Rainer.

I once owned a Golf 4 R32 and once a Passat B7 .
So, does that mean I can't access the CAN bus through the OBD port?

Hi,

The Golf 4 does not have CAN on the OBD connector at all.
"Similarly, with the Passat, nothing happens here except for vehicle diagnostics. That means you should locate the gateway control unit in these vehicles and tap into the corresponding CAN buses there."

Best regards, Rainer.

Okay, but as far as I know, the Golf 4 also has CAN, so I need to find the gateway there too .
What is the difference between CAN and diagnostic CAN?

Ak2113 wrote:

What is the difference between CAN and diagnostic CAN?

The connected control units and their messages, including the respective CAN bus speed (500 kbit/s or 100 kbit/s):
https://www.canhack.de/en/viewtopic.php?t=13

Best regards, Rainer.

So that's why I haven't received anything there .
Yes, but how do I get a value from the diagnostic CAN bus?
Do I need to send anything along with this?

In a nutshell, the following happens:

The engine control unit (ECU) is connected to the vehicle's CAN bus. This ECU constantly sends CAN messages onto the bus, which can be read and analyzed. However, to do this, you need to know the CAN ID used for specific data, such as the engine speed, along with the byte position and format in which it is transmitted. This information varies for each vehicle/model. That's why forums like this one are constantly filled with questions asking about CAN IDs for a particular vehicle (e.g., "Vehicle XYZ: Where can I find the CAN ID for measurement ABC?").

Initially, no data is transmitted on the diagnostic CAN bus; only when a diagnostic session is started (e.g., by VCDS) does any activity occur there.
Through this session, it is possible to specifically access the control units and, for example, read out measurement values or error codes.

Okay, thank you in advance .
But you don't know what I need to do to get an answer ).

Was that a question or a statement?

Ask Google about 'TP 2.0' .

Maybe it's still a little too difficult for me as a beginner .
I'm going to search for that on Google .
I've read so much, but I'm still not getting anywhere .

Don't be offended, but if you've read so much, I wonder why you don't know the difference between CAN and diagnostic CAN .

I always thought it was the same .
One spoke about the CAN bus, and the other about the diagnostic CAN .

You should first buy a textbook; "Bus systems in vehicle technology: Protocols, standards, and software architecture" is highly recommended.