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From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Experimental Ideas
Message-ID: <1462.UUL1.3#5129@willett.UUCP>
Date: 6 Aug 90 03:28:19 GMT
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 50

Category 3,  Topic 5
Message 40        Sat Aug 04, 1990
D.RUFFER [Dennis]            at 16:03 EDT
 
Re: ZAFAR ESSAK

 > the Allen Test Products "big thing-a-ma-jig" ...

Yes, many of the car manufacturers are including much of the diagnostic
capabilities right in the car now days.  However, these "diagnostic computers"
end up just making the problem of fixing the problem even more complex.  The
original ATP diagnostics that I developed are now only used in a last resort
when the manufacturer's "fault trees" do not find the problem.  Basically,
what happens is that the on-board computers monitor some built-in sensors like
oxygen in the tail-pipe, exhaust temp, primary voltage, battery amps/volts,
etc.  Then they produce codes that can direct the mechanic down a fault tree
to some more specific measurements that the mechanic can take.  Those
measurements take him further down the fault tree until he ends up determining
what part to replace (very few adjustments are made any more).  The most
common diagnostic, "replace the diagnostic computer". :-)

 > Is it possible to hook your PC to the car's computer and
 > interogate it on its performance, maybe even tweek it a little,
 > interactively even, without worrying about a 50,000 volt spike.
 > What kind of port is it anyway? Serial or parallel?

Yes, you can!  If I remember right, the connection typically is a 12 volt
serial bit stream.  There is usually a connector under the dash that you
connect to and typically you have to short two pins together before it starts
spitting data out at you.  Some systems dump just codes, others include their
measurements with the codes. Some of the most complex systems even accept
input from the connector to modify their parameters.  On the Cadalac, you have
a polled system where you have to tell it which one of the 6 (or more) onboard
computers you want to talk to.

All in all, you have enough variations on the connection schemes that you
still need a sophistocated computer to figure out how to talk to the on-board
computers.  The manufacturer's sell a "black box" that will talk to their
systems, but ATP's machines handle almost all of them.  Then, there is also
the problem of all the fault trees.  They have replaced the old fashoned
repair manuals with fault tree proceedures.  ATP has programmed them into
their machines so that they can walk the tree automatically for the mechanic,
telling him when to take measurements (if needed) and reporting the
conclusions on a form that they can present to the customer (to justify the
$1000 replacement of the diagnostic computer :-).

IMHO on-board computers have just made the problem worse.   DaR
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