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All OBD2 scanners I have used are solely using broadcast addressing when it comes to talking J1850 V(PWM). I wonder why this is so. If I understand the standard correctly, if 61 6A F1 (68 6A F1 for VPWM) is the usual OBD2 broadcast header, then 65 10 F1 (6C 10 F1 for VPWM) would be the proper header to address the first ECU.

Is that correct?

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  • For specifics, can you provide make, model, model year and photo of OBD connector showing which sockets are populated?
    – zipzit
    Apr 15, 2022 at 16:01

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Ahh... a fellow engineer hacker in the space. Me too. I will say this is not a specific answer to your question, but instead an introduction to the space for those who may be interested in what's happening in the background. I want to share a bit here. Not sure exactly where you are going, and what manufacturer, model and model year we're talking. I'm guessing you are talking Ford Motor, pre-2008 Calendar Year.

And for those who many not know, from mid 1990's to 2008 there were a whole lot of specifications (and differing pins on the connector) in use. Here's a nice reference.

Five OBD2 Protocol Types

From 2008 on CAN (Controller Area Network) [Spec ISO 15765-4 and SAE J1879] seems to be the standard.

This is beyond a pretty wack conversation. In my case, I'm investigating an anti-lock device based on ESP32 (Internet of Things Device) with read-only capability using 2021 Model Year CAN. And yeah, if you are a true tech geek the digital communications stack is bizarre.

CAN Communications Protocols

And this has been quite a journey. Hint, a great place to start is the stuff over at Sparkfun. They also sell connectors and UART boards. UART = Universal asynchronous receiver-transmitter, a hardware communication protocol that uses asynchronous serial communication with configurable speed.

https://www.youtube.com/watch?v=YvsGuK9Up0E SparkFun According to Pete #55 - How CAN BUS Works May 7, 2018 SparkFun Electronics

https://www.youtube.com/watch?v=GH1315H2SIc SparkFun According to Pete #56 - How OBD2 Works Jun 4, 2018 SparkFun Electronics

There is a lot of great stuff in the notes there, including stuff from Charlie Miller and Chris Valasek. I will say, the "Adventures in Automotive Networks and Control Units" is a nice article.

And yeah, I did not specifically address your detailed question. I was hoping a general introduction might be of help to others entering this space. In your case, what vehicle are you using for your testing?

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    I was on the cusp of closing this question because it is a bit outside of the expertise of most people on this Stack. I'm glad you've put up what you can and maybe if you rethink it, you could possibly add something more directly to the OP's question (It is my hope, anyways!). +1, nonetheless :o) Apr 15, 2022 at 15:56

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