OBD-II/J1850/VPW/class 2/whatever SNIFFER

**Rickertsen2** · 07-07-2005, 12:42 AM

this is realted to Class 2 data bus? J1850?

Since i cannot find the info i am looking for i will have to do some reverse engineering myself. I need a sniffer that is capable of capturing raw bus data for analysis. I am NOT talking about a scantool and i am NOT talking about a tuner or flasher. Does anybody have any info on this? I havn't researched it thouroughly but it looks like the elm chip can do this and will be perfect but i will have to write my own software unless anybody knows of any existing software with raw packet sniffing functionality.

**chewwtoy** · 07-13-2005, 09:45 PM

You could always spring $1995 to buy a neoVI. (www.intrepidcs.com). It is bundled with software that will allow you to read raw data from the bus to reverse engineer J1850, CAN, LIN, ISO9141 and others. But this tool is generaly sold to engineers who porgram the ECUs that go into vehicles.

You can also write you own program if you don't like it. You can download it for free at their website, but it won't do you anygood without the hardware.

**Rickertsen2** · 07-21-2005, 05:55 PM

Wow!! That price is nuts. I don't think i can afford that. I'm going to build my own once i get my car back from the body shop.

**Curiosity** · 07-22-2005, 06:28 AM

I'm not positive, but I think you're on the right track with the ELM. Expect each byte to be interleaved between the car and the scantool though. At least that's how I assume it will look.

**Rickertsen2** · 07-22-2005, 07:55 PM

I just finished reading through the ELM datasheet and it looks like the ELM chip can be put into a variety of sniffer modes and do exactly what i need. For now this project is on hold because my car is in the shop after being in an accident

**Curiosity** · 07-23-2005, 08:35 AM

You may find sniffing to be a waste of time. All you really need to do is send each mode/pid, read the result back and convert it to something readable. You won't really see anything special watching a scantool.

**Rickertsen2** · 07-25-2005, 10:28 PM

I plan to write a java program that will put the elm into a mode where it will monitor ALL traffic. It will then generate a list of physical addresses if sees activity from. From there i can look at the list in one of the links posted earlier and figure out which are likely to be the BCM etc. Iwill then set the ELM to monitor transmissions to/from the modules i am interested in one at a time and do things that should stimulate the messages i am looking for.