Open source GM OBD2 flash tool using a ELM327 device

[vn5000]

Looking good .
I have finished socketing my 0411 pcm ,so if you want something tested let me know.

[uknomeprk]

Have been taking a break from this ill be back at it soon. I'm going to pick up a second elm and run the 2 in tandem to monitor all traffic to see whats really going on. Also thanks vn5000 i'm sure something will pop up soon enough.

[antus]

It looks like elm 327 is no good for flashing because it has a maximum packet size (transmit) of 8 bytes which is not enough to get the process started.

Scantool.net are talking to their firmware developers and are considering making it possible with a firmware update on their newer stn1100 chip. They did not previously realise there was a need. Will update this thread when theres more news.

[uknomeprk]

Down but not out... First an update, no real progress has been made with GMOS (been very busy) but the idea is still alive. If a flash is not possible... is a slow reprogram? If nothing else we can use our collective knowledge, experience, and databases to compile the best of the best information for the future.

We have a lot of good info here, we know we can modify and control the PCM via VPW. Personally I'm going to give this one more big push and see what I/we can do. If absolutely nothing else we'll know what we need from the chip builders like ELM and be able to convey the message.

[antus]

The STN1110 developers were saying they could develop the functionality, but that has died out and they have closed my support ticket.

Im thinking this interface now: http://www.mictronics.de/projects/j1850-vpw-interface/

GPL firmware source code is in the firmware zip and the TX message size limit is present but it doesnt look like there is any reason why it cant be expanded to use whatever ram is available. It probably would be possible to compile the firmware for an atmel with more resources too. I probably wont have time to look in to this until next year, though. Anyone wanna build up a small run of these?

I'll attach the pdf and the zip here incase the original site dissapears. Thanks to Michael Wolf for creating this board and firmware and especially for releasing under an open source license!

If you decide to use this, check the above site for more information and possibly newer releases.

[uknomeprk]

2 big problems with the ELM327.
1.The ELM only receives messages from the header you set with the PP command or the header you send. This means when your looking for a response it wont be there unless you know where to look sometimes.
2. Lack of a RAW mode... this could and would streamline a lot of code.

Oh and buffer size so 3

[bwb1029]

I've been reading through the post and I understand some but most I'm a little lost. I have a 2000 Tahoe 5.7 and I'm wanting to save the exsisting tune and reflash it later. I was planning on using tuner pro and the elm327 w/ baud rate at 38400. It looks like you guys said you can do it one line at a time. How many lines are there how long would that take. It has a tune on it now but for 93 Oct so I want to put a stock on and be able to go back later if needed. If I can get both tunes side by side I could compare the difference and let you guys know, so we would know what lines to change and what to change them to for a basic tune. Thanks for the help anyone close to Pensacola FL?

[antus]

If its a 93 then it probably is not an OBD2 pcm. What is the service number of the ECU? We found that OBD2 flashing is not possible with the elm because it can not transmit data packets long enough.

[bwb1029]

OK thanks, its a 2000 with a 93 octane tune

[antus]

Haha, sorry was working on 2 things at once. Looked up to check the date, and interpreted 93 Oct at October 1993!