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This article was posted to the Usenet group alt.hackers in 1995; any technical information is probably outdated.

Connecting a PC to a car's onboard computer

Article: 7834 of alt.hackers
Newsgroups: alt.hackers
From: (Chad Beeder)
Subject: Connecting a PC to a car's onboard computer
Sender: (News User Id)
Organization: Eskimo North (206) For-Ever
Date: Sun, 14 May 1995 00:54:00 GMT
Approved: Of course
Lines: 24
Status: RO

My brother has an old 8088 laptop computer lying around.  We were thinking
it would be a cool hack to wire it up to his car's onboard computer so it
could be used to display fuel effeciency, speed, and whatever other info
we could get out of the thing.  We found the connection to the car's
computer; it appears to have four pins, one of which seems to be ground,
two which according to a voltmeter have around +5 volts, and another which
doesn't register anything on the meter.  Does anyone know where we could
find information on the pinouts, baud rate, command set, etc. for this
thing?  We checked the local library but didn't turn anything up.  The
car is a 1990 Geo Metro.  (Well, you use what you've got...)

ObHack:  When working on getting a new phone line wired for my computer,
we were standing out by the phone junction box (or whatever it's called)
outside the house.  Not knowing which pair of screws the phone line was
connected to, and not having one of those lineman handsets, we just did
the next best thing: we took a little P.A. type speaker we had lying
around, took the exposed leads of the speaker and touched them to the
lines, and then listened for the (very quiet) dial tone in the speaker.
Dialing was accomplished by rapidly tapping one lead of the speaker to the
line to simulate pulse dialing.  It actually worked, too.
   -        - "...And everything under the sun is in tune,  -
  - Syzygy - but the sun is eclipsed by the moon."         -
 -        -                             -

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