Multiple OBD2 connections
Thread Starter
Instructor
Joined: May 2009
Posts: 118
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From: Waltham MA
Multiple OBD2 connections
Been thinking about the possibility of connecting multiple OBD2 devices (like a window valet and a smartphone interface). Physical connector issues aside, has somebody done that electrically? If I read the OBD2 standard correctly, GM was using SAE J1850 VPW which has a CSMA/NDA arbitration scheme and therefore should be capable of handling multiple connections to the bus...
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
There are several companies that sell Adaptors to allow multiple OBDII devices on the buss at the same time. I have not done it but researched it once and got involved in a post that discussed it.
BC
BC
Thread Starter
Instructor
Joined: May 2009
Posts: 118
Likes: 3
From: Waltham MA
Thanks, Bill! I was looking for a commercially available solution but couldn't find one, that's why I was asking.
Probably using the wrong search terms. Do you have something you can point me towards?
Probably using the wrong search terms. Do you have something you can point me towards?
Thread Starter
Instructor
Joined: May 2009
Posts: 118
Likes: 3
From: Waltham MA
Never mind - it's called an OBD2 SPLITTER (d'oh!) and Amazon has one:
http://www.amazon.com/OBDII-Splitter.../dp/B000TMCX72
http://www.amazon.com/OBDII-Splitter.../dp/B000TMCX72
Racer
Joined: Feb 2004
Posts: 359
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From: St. Paul MN
Todd
Thread Starter
Instructor
Joined: May 2009
Posts: 118
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From: Waltham MA
You are correct, the OBD bus is a one-wire shared bus with arbitration to avoid packet loss. There are already 10+ computers on the OBD bus with room for more. You can tap in anywhere from the passenger footwell "star connector", or any endpoint connection like the RFA or door modules, whatever is convenient. A y-splitter in the dash's OBD port should also give you power & ground which are usually necessary for those devices.
Todd
Todd
For those following this thread, splitters and right angle adapters are also available for cheap on eBay. It's amazing what you can find if you use the right keywords!
