> > 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.
>
> They are secrets, to lock you to the dealership for repairs. Even OBD-II
> does not include ABS as part of the standard, it is manufacturer-specific.
>
> However, diagnostic info is not always accurate. My wife's car presented
> the error code "EGR vacuum valve solenoid has high resistance". Although
> it seemed to function OK, I assumed it had an intermittent open, so I
> replaced it and reset - same trouble code came back. I tested everything,
> the valve functions in the car just as it should. I disassembled the
> engine control unit, and looked at the circuitry that drives the EGR
> vacuum solenoid - there was no way it could detect the current, it was
> just a Darlington to ground, no voltage sensing or emitter resistor. The
> positive feed was to a common bus with other outputs. A friend in the
> industry suggested that the codes often are indirect and further down a
> diagnostic flow chart, and as such, are not always accurate. He said that
> more likely the ECU expects some change in engine vacuum or oxygen sensor
> output when it triggers the EGR valve, and it wasn't seeing it. I finally
> tracked it down to a stuck mechanical advance in the distributor.
>
> So, my opinion of onboard diagnostics - not so good. Quite often the
> result is a wild goose chase.
>
> Cheerful regards,
>
> Bob
>
>
>
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>
>I got the "auto-Enginuity" scanner, which works on everything, and talks to
>my PC, and the palm-pilot (with serial port!)
>
>Works great on all makes I've tried it on, ford, buick, chevy..
>
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>
>I think it's less benign than that - yes, they allow themselves to become
>lazy, but they make money on parts, and use the tool as a way to fleece
>the customers. "The computer said the part was bad, so the part was bad".
>
>My motto is, if I can't fix it myself, I'll buy a new car. No garages for me.
>
>Cheerful regards,
>
>Bob

> > Like any diagnostic tool, the result requires interpretation.  The
> > diagnostic codes are usefull, but as you have found, does not make
> > experienced engineers redundant.  Unfortunately many garages do not
> > understand this, and take diagnostic codes as gospel, replacing sensors
> > that
> > are operating perfectly well and charging the customer for their lack of
> > experience.
>
>I think it's less benign than that - yes, they allow themselves to become
>lazy, but they make money on parts, and use the tool as a way to fleece
>the customers. "The computer said the part was bad, so the part was bad".
>
>My motto is, if I can't fix it myself, I'll buy a new car. No garages for me.
>
>Cheerful regards,
>
>Bob