j2534 Open Source Resources

[KerchumA222]

THANK YOU SO MUCH! That is exactly what I was looking for/needed! Now I can make mroe progress in my freetime.

[Tazzi]

THANK YOU SO MUCH! That is exactly what I was looking for/needed! Now I can make mroe progress in my freetime.

Note quite exactly, but sounds like your looking to building a custom VPW device. Currently Im looking at the arduino avenue for this. Im sure this could easily enough have 4x mode and block mode added?

Looks like amost everything on VPW uses standard 12byte messages. This only changes when we reach 4x mode where we need to start sending messages of 1000+ bytes ect. So really it should be too difficult to do, as long as we know how bit the message is that we expect to receive and send.

[KerchumA222]

@Tazzi
J2534 (when J1850VPW is supported) allows for 4k transfers. The PassThruIoctl function needs called to change the mode to high speed for programming, but it appears to be independent of frame size (which is always at a maximum of 4096 bytes PLUS headers). Also, I am not building a custom device. The point of this spec is to make it easy to write software for multiple devices. I am using a generic J2534 PassThru device designed for a Toyota. My device reports that it supports j1850vpw j1850pwm CAN and others so it should be sufficient.


I have a question for everyone on here: Can a DELCO PCM be programmed using CANBus (assuming the vehicle supports the protocol of course)? It has much faster transfer speeds than VPW. Also, we can have more than one connection open in the same interface as long as the physical pins the connection uses don't overlap. CAN and VPW don't overlap.

I plan on starting my work on this in about 2 weeks (After Finals week). I will build the skeleton (Objected Oriented C++) and upload it to a sourceforge or github or something so others can see/work on it.
EDIT: Forgot to mention, my skeleton will be 64-bit compatible. So far it looks like only the registry access has to be altered slightly for that to work.

[ejukated]

Interesting project! Newer ECMs 2006+ are CAN

[antus]

Delco pcms are generally the older ALDL ones. The first early LS1 pcm was VPW and still branded delco, but I dont think we got that one in australia. Then they turned in to delphi. The commodores have 2 buses, they kept ALDL for a long time to keep the price down for the modules like abs etc, but they had VPW and then CAN for the pcm. I am not aware of any car which has both at the same time. Its VPW+ALDL or CAN+ALDL or GM-LAN (can + ??) Not sure if the low speed bus in GM-LAN is still ALDL or not.

[KerchumA222]

It looks like GM-LAN is just CAN (ISO 15765-2). Looks like they dropped the low speed bus altogether.

I am still working on this project... slowly. I acquired a PCM from a 2001 Sunfire to play with. Anyone have any insight on how to set a PCM up on the bench for tinkering?

[KerchumA222]

Also, should I create a Windows COM wrapper for J2534 and make it act like ELM? That way you could use the same cable for just about everything. (it would share a common library for J2534 functions with the other [reflashing] program.

Also, Antus, the link you posted before with the 1997 pcm... is the code they provided for the bootloader 32bit (not HC11)? If so couldn't i just unlocked the PCM and begin download mode and execute the bootloader?

[Taylor]

Interesting project.

Question, where do you source interface for $25?


For wiring of the ecu, you will need to trace wiring diagram for that year, power + ground + switch, and hook up CanH and CanL.

As for comm's id work on generic OBD first with your interface as thats pretty much the same for alot of ecu. Then work on the properietary gmlan stuff.

[antus]

@kerchuma222. Yeah thats the idea. Bootloader needs to be right for the hardware though. Anything but one size fits all.

[KerchumA222]

@Taylor I ebayed the $25 J2534 VCI. It is listed to work with Toyotas. The idea behind this is that no wiring is necessary because I intend to program the PCM the same way a dealer would upgrade the PCM software. They simply plug into the OBDII port (I'm in the U.S. so its standard), connect over J1850VPW (Or GM-LAN with is just a superset of CAN and I believe its supported by the J2534 unit I have), and then send their Manufacturer specific commands/code and upload the new software.

@antus If I am focusing on a particular vehicle would this be easier to accomplish? And does it sound feasible to query the PCM via OBDII to figure out what software (an as such the hardware) its running to determine compatibility automatically (in a program that is, something I would release to everyone here). I know GM PCMs have some way of detecting themselves... I might have to sniff the bus while updating my car and see what sort of communication happens.

And to anyone else who is still debating if this is possible: GMTIS allows me to update my car using the cable I have... so its only a matter of making a free program to accomplish the same thing.