ecm coding

[cobaltssoverbooster]

what is the name of the coding in the ecm called. how to read it and stuff like that interests me, i want to check it out. i will most likely not be pro at it but i like to put my toes in the water lol

i know i know

[dimented24x7]

The code itself is actually stored as machine code. These are the instructions that basically 'tell' the processor what to do. Typically, the calibration (constants) is stored at the head of the code, followed by the operating system. The actual software code is written in a variant of C++ and then compiled. To read the code, you need to first find out what processor is in use, and then disassemble the code into assembly, which is basically a human friendly way of representing the machine code. Next, you need to locate the OBD serial data controller and use that, along with the OBD-II data and DTCs, to start locating the various parameters within the memory map. Such things as the engine RPM, mass airflow, spark advance, etc. Once you have that, then you can begin to look at the code and find the various constants and tables. Heres a summary of what steps are required to get into the PCMs mind: http://www.thirdgen.org/techboard/di...-101-step.html. The concept is easy enough, but its exceedingly difficult to put into practice. The PCMs follow Moore's law, meaning that as time progresses, they get exponentially more complex.

I started working on these back when the old 8-bit ECMs where still popular, and people hadn't really started with the later PCMs yet. Those where easy to figure out. Take for example the early TBI computers. The ROMs where small, and the code would be < 10,000 lines. Took maybe a month to map one out, working on it every now and then. The later TPI computers where a little more complex, maybe a couple months to map one out. After that was the moto 68HC11 based PCMs. More complicated as tehy also had e-trans control as well. Took about 6 months to map one out. After that is teh early OBD-II PCMs based on the M68332. Takes well over a year to work through one of these. If you notice, the time frame in years it took for me to figure out the code goes: .08, .3, .5, 1.5 years. This is also exponential, and in mathematics, is called non-polynomial time. This means there no easy short cuts to 'figure it out' with the later computers. The learning curve for these is basically a vertical line, so great patience is required when your first starting out. If you really want to get into it, look at a lot of the earlier hacks floating around on the 'net for the GM ECMs with part numbers contaning the last 4 digits 7747, 7730, 7749. Those will give you a good introduction to what the engine controller logic looks like inside.

[shabby]

Start coding...

[cobaltssoverbooster]

shabb thats not funny this is actually interesting, i mean sure i wont read and figure out my own but i know whats going on more than the average if i at least get a basic goin. thanks dimented

[cobaltssoverbooster]

what would you use to read the hex of an obd 2 car?

[fr0stb1t3]

what would you use to read the hex of an obd 2 car?

Google is your friend.

[dimented24x7]

The easiest way to get the binary is to remove the flash chip and place it in a reader. These can be had for < $300 (see my post on how to do it). Many tuner packages (HP tuners included) encrypt the bins so you cant read them. In some cases its possible to get the whole binary thru the OBD port, but this requires you to present a valid key, which means you need to know what security algo is in use. There are at least a couple dozen different algos to my knowledge.

To look at the actual hex, you can use an editor like hex workshop or hex editor neo. To turn a binary into assembly, you will need to first find out what processor the PCM uses. This is sometimes easier said than done as the processors are custom made for GM, and sometimes only bear a GM part number. Once you have that, than you need to find a disassembler. Sometimes there are freeware ones offered by third parties or the manufacturer, but other times theres little support. Datarescue's IDA supports a lot of different processors, but is very $$$.

[cobaltssoverbooster]

wow this hex stuff is awesome so security locked down its amazing!

[mecanicman]

Dimented24/7, were can I find this how to post? did a search, but no luck.

[cobaltssoverbooster]

http://www.thirdgen.org/techboard/di...-101-step.html
i belive he had a link for more on the how to in there