4cly: What has / can be done?

[Guest]

Hi All,

I'm an electronics engineering student planning a major design project for the upcoming fall. My group is considering an OBD-II scanner tool, with a nice gui, etc.

Rather than just reading trouble codes and sensor outputs, I'm more interested in modifying tables, etc. I have a '99 Z24 that would be the guinea pig for this. However, based on posts here and at the org, I'm confused as to what's possible and what has already been done.

Is it possible to do writes over the OBDII interface, or has it even been tried, etc? Some people seem to think it's impossible, but I've yet to find evidence to actually back that up. I would very much appreciate if you could help get this newb up to speed.

Thanks!

[RoboGeek]

yup. Its possible to do. Thats the way GM changes cal files when the reflash.
A few people have developed ways to do it with software (LS1 Edit, etc) but they are specific to that model.

The info floating around on JBO is so screwed up I only jump in there now if somebody is really about to screw something up bad. Most of those guys, even if they could flash the PCM, have no idea how to even tune a car. Look at how many people blow their motors over there from running too lean with NO2 and boost.

Hang around and you'll pick up on just what everybody here is working on. We are all on our own little projects but someday we may just organize a collective effort and make an open-source program.

[Keith@HPTuners]

Hi Joe, building a scan tool software is much easier than one capable of reflashing the tables.

If you're looking to build a interface, elm makes some nice interface chips and boards that you can assemble/modify to your likeing.

To write the software, there is already a good amount of information regarding that on this site... protocol, messages, etc. etc.

If you didn't want to build your own interface you could go with a pre-built B&B LDV device or even try to hack your own converter cable together... voltages may get a little screwy though from the com port. I haven't looked into that too much.

So, how much work are you guys looking to do?

- Keith

[jdudas]

Hi Guys, thanks for the warm welcome and the wealth of information this site has provided.

I think I have a much better understanding of the whole OBD-ii system now - at the lower layers, anyway - so I've got a few questions . I'm mostly confused as to how much of the information I'm finding here about programing the LS1 PCM computer applies to my module. You guys have done a lot of work in the Flash Writing thread, and I'd really like to build upon that.

Just to give you an idea, my group consists of 5 electronics engineering students, committed to working on this project in an almost full time capacity for about 3.5 months. We're all familiar with uControllers of various flavours and have degrees of hardware and software design experience. I'd like to make this a fairly in-depth project, so doing the J1850 communications from scratch (I'm thinkin an Atmel AVR or PIC would be awesome for this) with the giant buffer you guys were talking about would be interesting. I envision an in-dash graphical interface on a touch-screen (for flair, that's about it) to round out the technical merrits of the project. But I think the PCM programming is what would make this the most interesting and unique, which is important to us. Any suggestions you may have are appreciated, and we'll do our best to share the results.

What I've gathered so far: Programming is possible (hence table changes for the 2.4L GM S/C) but it's a proprietary GM system. We have no official documentation, but it looks like there's a boot loader residing on the PCM which will accept an OBD-ii command to start writing over program code. Has GM ever officially released information about this? Also, are there any commercial products, besides GM's own Tech-2 that are capable of doing this sort of programming?

[Keith@HPTuners]

Hi Joe, what's the latest?

GM doesn't release info.. AFAIK..

Ease does put out a programmer as well similar to GM's programming system.

[sean]

Ease does put out a programmer as well similar to GM's programming system.

its just a basic software with gm sps interface also requires the use of the gm cd as well.