Attila Muhi writes:

> I know, this is off topic, but I have tried Google, and have no idea where to search for this...
>
> I need the pinout for the diagnostic plug in my car. I have some
> trouble with the ABS brakes, and want to retrieve the fault code. As
> far as I know a slow pulse train should be available somewhere in
> that plug.... Probably I won't need a pic to read the pulse train
> :-) , just a led or a scope. But which pin, and how do I interpret
> the code ?
>
> This seems to be a well hidden secret. !!!  Btw, it's a MB diesel,
> year 1994.

This is one of the current scams in the auto industry.  The auto
manufacturers are keeping their diagnostic codes secret so (1) they
can profit by selling disgnostic hardware and software (2) they can
help their dealers by only supplying the dealers with the tools
required to disgnose problems in the car.

There are some 3rd party companies that reverse engineer the codes,
but even their products (hardware and software updates) are rather
expensive.  Many auto shops will charge $50-$100 just to hook your car
up to the computer and give you a reading!  Already gone are the days
of the "free estimate" when the computers are involved.

I believe there are actually several lawsuits regarding this.  I have
a recollection of one group suing the automakers to make their
disgnostic codes public, and I wouldn't be surprised if the auto
companies are using the DMCA to shut down the makers of 3rd-party
diagnostic gear.

That said, there may be a simple solution.  The "Auto Zone" chain in
the US has the diagnostic tools and software for many automobiles, and
they will give you a *free* diagnostic report.  However, their tools
are a bit on the basic side.  I was diagnosing a "check engine" light
problem that I was almost certain was an oxygen sensor fault.  When I
plugged into the Auto Zone computer, it did indeed confirm that the
oxygen sensor was at fault, but the software could not tell me which
of the two oxygen sensors had failed.  At $50 for one sensor and $90
for the other, it's no small matter to simply replace both!  Further
investigation revealed that the problem was not with either sensor,
but that one of the wires to sensor had chaffed through midway between
the wiring harness and sensor itself.

-p.
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist