CAN Bus issues

On a vehicle CANbus there are several types of message.

Most of the traffic on the CANbus is the data being sent from modules and being received by other modules. You don't need to ask for that data, it will just be there all the time that the car is on.

The CANbus is also used to send diagnostic messages. A tester will send a request to a particular module, and that module will respond. Messages like that are not usually present while the car is in normal use, but these diagnostic messages are often used by aftermarket devices.

Have you got a way of seeing if the ordinary messages are there? The CAN-H should be between 2.5 V and 3.5 V, and the CAN-L should be between 1.5 V and 2,5 V. If the voltages are the same, there are no messages being sent.

Have you got an oscilloscope to look at the voltages?

I will borrow a scope for testing the voltage. Thanks so much for your reply.
So I want really to get the steering position and the velocity. For that what should I use ? OBD? and is it a must to send a msg to get these data from the ECU Modules ?

ahmedragia21 said:

I will borrow a scope for testing the voltage. Thanks so much for your reply.
So I want really to get the steering position and the velocity. For that what should I use ? OBD? and is it a must to send a msg to get these data from the ECU Modules ?

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It's very difficult to know what signals are available. It varies a lot on different cars.