NefMoto

Technical => Reverse Engineering => Topic started by: morfej on March 27, 2012, 10:39:12 PM



Title: Snooping OBD communication
Post by: morfej on March 27, 2012, 10:39:12 PM
Hi,

At topic test equipement I notice that "OBD Y splitter cable for snooping OBD communication" is mentioned.

I want to ask if snoop KWP2000 protocol on a desk for example airbag ECU connected to diagnostic (CLIP).

Is it safe to connect KKL cable in parallel (K-line,+12V,GND) and try to monitor communication in a terminal ?

How do others snoop OBD communication ?

br


Title: Re: Snooping OBD communication
Post by: setzi62 on March 29, 2012, 08:19:33 AM
You can monitor OBD communication with a second K-line/serial converter cable and
a connected terminal program, but you need to be able to set the correct communication speed.
And you will not be able to monitor the slowinit/fastinit patterns on the line.

Best way in my opinion is to use a logic analyzer and a voltage converter 12V->5V (two resistors are fine).
The Saleae Logic Analyzer is very good, the data collection unit just connects via USB to a regular PC,
so you can log a very long time with high resolution and the data analysis application can decode
serial data.

See here: http://nefariousmotorsports.com/forum/index.php?topic=568.msg4523#msg4523


Title: Re: Snooping OBD communication
Post by: morfej on March 30, 2012, 05:16:47 AM
Communication speed was ok setting 10400 bps for KWP2000 for the thing I monitoring.

The hardest thing is that you get data from sender and receiver all together, so it's not so easy to understand what's going on. I'm doing step by step sending commands to ECU and rending replays to dignostic. Slow steps firste :)

Br