OBD2 serial port connections

ydeardorff · Initiate Jedi Joined: 02 Jan 2011 Posts: 32

Hello all,
Its been awhile since Ive been here.

Im installing a 05 Subaru EJ20 turbo into my sterling kit car. What im interested in is, I have installed an entire 03 WRX wiring harness in this car and dumped the EZ wiring harness.
How many connections can be wired into the OBD2 serial port?

Id like to run a hud, and a blue tooth connection using OBD auto doctor on my in dash info-tainment tablet, but still leave the port accessible for diagnostics if needed.

Can multiple items use this connection at the same time? Or can they only use one connection at a time? If only one at a time, is there way to make multiple connections via a bluetooth system?
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Sterling Kit car (VW based) Project

Current donor car and engine:
2005 WRX Turbo

Looking for 200 to 250HP lump, Found it = WRX

andymcc · Posted: Sun Dec 28, 2014 4:05 pm Post subject:

On my 2000MY I have both ISO K-Line and Subaru SSM Tx/Rx on the OBD port, but it's not OBD-II compliant (UK model).

Both K-line and SSM are shared-wire, eg. multiple devices piggy-back the line, but only one can Tx or Rx at a time. eg. you could not have both a Scangauge and Diag software on a PC communicating with the ECU at the same time.

OBD Pinout (YMMV)

Subaru Pin # ISO Pin #
1 16 Battery 12v Red
2 15 L-Line ISO 9141-2
3 14 Can Low J-2284
4 13 SSM - Tx (5v TTL) Green/White
5 12 SSM - Rx (5v TTL) Light Green/Red
6 11
7 10
8 9
9 8
10 7 K-Line ISO 9141-2
11 6 Can High J-2284
12 5 Engine ground Black/Red
13 4 Engine ground Black/Red
14 3
15 2
16 1
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1990 VW 252 EJ25
1990 VW 246 AFN

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