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gomi_otaku
gomi_otaku, Technician
Category: Car
Satisfied Customers: 3457
Experience:  VW Technician, VW FastTrack, VW Academy, VW Certified
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Where can I find the OBD computer version on the CAN BUS ?

Customer Question

Where can I find the OBD computer version on the CAN BUS ?
Submitted: 5 years ago.
Category: Car
Expert:  GM Tech (Cam) replied 5 years ago.

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

What car are you working on?

Customer :

This is a general question, if the software version appears on the CAN BUS and can tell about the structure of the BUS ?

Customer :

Different models of same manufacture has different bus structure (like Ford Focus and Ford Mondeo). Sometime even the same car model has different structure (depending on engine type). I wonder if there is a way (like using the sw version) that can uniquly identifies the bus structure

GM Tech (Cam) :

Well, in the GM system, the bus is a high speed bus with a twisted pair running at a voltage of 2.5V, and it is a loop with a terminating resistor in different modules or a stand alone resistor. This should be standard for the CAN OBD 2

Customer :

It is not. There are some parameters that reside in different places

GM Tech (Cam) :

it is not what?

Customer: replied 5 years ago.

The OBD2 is standard but is being implemented differently by various car makers. Thus the BUS structure is not alike various models and various makers.

 

Expert:  gomi_otaku replied 5 years ago.
CAN-BUS is a standardized system- what differs in models and manufacturers is how many BUSes they have, and how those BUSes are connected together by a central diagnostic module that allows communication to the scan tool. In addition, some vehicles will also have LIN BUSes for master/slave relationships between modules (such as running a wiper control module off a body control module) and some newer systems are also using what is called a MOST BUS or a fiber optic ring. And there is nothing that really pops up on a scan tool to tell you what kind of system you are working with, that is why dealers invest so much in training their techs. it's not something where one person can know every system intricately.