iso 9141 k line sniffing

Discussion and research on OBDII integration, especially on OEM specific PIDs from Ford, GM, Chevrolet, BMW, Porsche, Audi, Toyota, Volkswagen, Mazda, Honda, Subaru, Mitsubishi and others.
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Billy C
Posts: 31
Joined: Thu Jan 03, 2013 2:11 am

iso 9141 k line sniffing

Post by Billy C »

Working on a 2002 toyota MR2. It doesn't have a traditional can bus and the OBDII uses the older 9141 K line single wire. I'd like to use the legacy OBDII adapter to convert a few channels of information to traditional can. How does the legacy OBDII adapter work exactly? Would I be able to use it without the race capture pro and pull data out of the can stream coming from the OBDII adapter or does it require some kind of command to pull data off the OBD K line? If so, once the data comes from the K line, what defines the can channel it ends up on? Is there mapping built into the firmware of the adapter that directs this data?

I'm just getting into can a little more and would like some more info.
-Billy C

brentp
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Post by brentp »

Hi,

Here's the info page on the OBDII adapter: https://wiki.autosportlabs.com/OBD2CAN

It's operation is straightforward:

It makes a legacy OBDII interface appear as if it is a CAN bus OBDII interface. It will translate a CAN OBDII query into the appropriate legacy OBDII query, and then translate the legacy OBDII response back into a CAN OBDII response.

It will operate as fast as the legacy OBDII interface allows. RaceCapture will only query the next PID when the current PID is complete.

We have found that other systems, like MoTeC , will blindly query CAN OBDII at 50Hz, which will cause problems with the legacy OBDII adapter, since legacy ECUs are typically much slower (7-10hz).

Hope this helps!
Brent Picasso
CEO and Founder, Autosport Labs
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Billy C
Posts: 31
Joined: Thu Jan 03, 2013 2:11 am

Post by Billy C »

Are the OBDII can mapping channels standardized for things like TPS, Coolant, MAP... ?


In this example how would I know what can channel to look for TPS on?
TPS OBD_CAN ---> LEGACY ADAPTER ---> KLINE OBDII TPS ---> LEGACY ADAPTER ---> TPS OBD_CAN


Sorry if this is beginner stuff here
-Billy C

brentp
Site Admin
Posts: 6281
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Yes, these are all SAE standard OBDII PIDs. You can see a reference for all standard PIDs here:
https://en.wikipedia.org/wiki/OBD-II_PIDs

Note, not all ECUs implement all standard PIDs, but RPM, EngineTemp, TPS and a few more are almost always present.
Brent Picasso
CEO and Founder, Autosport Labs
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