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Comment by Bro_Merch | Hacker News Reader

@klez

What exactly do you do? The reason I ask is because 50 hours a week I'm an Auto Tech. The remaining hours that I'm awake I code. This week my project has been reverse engineering a pc based scanner that I have to learn about how it interacts with OBDII / CAN in an attempt to make a super tool that gives me specific abilities. The people I deal with during day know nothing of computers and the people I deal with at night know nothing of cars.

You are the first person that I have ever heard mention both in the same post.

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This is pretty off-topic from the OP, but I want to point out that the ISO standard for OBD-II is a fantastic reference for this kind of project. We built an OBD-II reader for our engineering capstone project, and that ISO standard was an invaluable resource for getting things to work.

If there's a university nearby, you might want to go check out their engineering library and see if they have a copy. I don't recall the ISO number off the top of my head. If you're really serious about the project, I think the book only costs around $400 or so.

Most of the "super abilities" provided by high-end scan tool / ECU flash packages work by using manufacturer-specific data sent over the CAN bus, not OBD-II itself.

Some newer and higher-end cars even use proprietary crypto keyed off of the VIN number and a shared secret to protect from access by third-party tools. There's a good-sized cottage industry in breaking proprietary ECU protocols and crypto, because there's a solid niche market in selling mechanics one $20,000 "multiflash" tool to replace their ten $10000 manufacturer-provided "diagnostic systems," especially in the high-end exotic market.

I was able to find enough resource online to build an ISO OBD-II scanner as my seventh-grade final project, without needing to resort to hunting down the standard. Today there are even open-source projects like http://en.wikipedia.org/wiki/OBDuino which can provide a solid code-based understanding of the three old OBD signaling types (PWM, VPW, ISO), as well as the basic protocol.

I'll let you all get back to topic at hand. I have to say thanks though. I never imagined getting so much helpful info. The super ability I seek seems like it would be in a less secure area because even cheap hardware store tools can do it. I am trying to remove, relocate, or hide fault codes without resetting the emissions monitors. That way as a hush hush marketing ploy of my business I can truly "guarantee to pass" and depending on the solution possibly guarantee to never fail again.

I hit an idea slump in my normal utility making and decided to put my otherwise wasted time to use.

Thanks Again ~

Of all the car I worked on (mostly Mitsubishi and Ssangyong) very few of them had non-standard procedures for erasing DTCs.

I don't know what you mean by 'erasing the emission monitor', unless you mean the freeze frame, which usually gets erased when you erase DTCs with the standard 0x14 request.

Anyway I work exactly as you do, by reverse-engineering official tools.

And I'm not very knowledgeable about cars anyway :)

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