http://obddiagnostics.com/index.html
You might want to check this out. I bought this interface a couple of years
ago and it has served me well on both of my american cars and my 95 SL320.
You can only access the powertrain trouble codes for MB. For the other MB
proprietary codes such as ABS etc. you need to spend a lot more money on
some upscale systems like Sun etc. The Diagnostic DVD's I have seen are only
listings of trouble codes which you can get for free on the internet. For
example the site for MB codes is
http://www.carsoftwares.com/mercedestroublecodes.html
Peter

Some more info that I ran across during my research
http://pages.prodigy.net/jforgione/MB_S500.html

I bought a $99 code reader which gave me a code. Then I went to dealer,
told them the PO170 code and asked them to tell me what was, in fact
wrong. $70 later they said Mass Air Meter was bad and it would cost
about $500 - $600 to replace. I went home, looked on the internet found
part for $280 but decided to try cleaning the original. I removed it
cleaned it, replaced it and so far......... it's been OK.

So, the code reader gives you some information but not the full picture.
Spending $99 saved me $500 or at least $280. Knowledge is power; a code
reader points one in the right direction.

Incidently, the plug in port is near the hood release.

If you have the code reader, you can buy a year subscription to alldata.com
for 24.95 and it explains the codes and where to locat the part on the car,
(among other things for troubleshooting). Cheaper than the shop manual.

As a computer geek, and tech freak, I am more grateful every day
for my two 300D's - my diagnostic kit is a 12v test light, a $14
Radio Shack multimeter, and, oh yes - a vacuum guage ;-)

Absolutely. When folks at the tavern admire your new Benz,
you can nod wisely and say, "Oh by the way - I also have
the diagnostic DVD set". This alone will cause women to
jump into your trousers. Honest.

Is "practical" really the concept we're seeking with the
latest IBM/Microsoft/Chrysler/Benzes?

Seriously, though, the value of the investment you make
in tools and information is directly proportionate to your
abilities, your willingness to use those abilities, and
your knowledge.

My brother is a gifted artist. I am unable to draw a straight
line with a ruler. My entire set of artistic tools consists
of a ballpoint pen - the same one I use to pay bills with.
Conversely, my brother could (and has) seriously injure himself
and any innocent bystanders with a common screwdriver. He
has no business with any mechanical tool more complex than
a spoon, and I have no business with a complete set of lama-
hair brushes. The most important knowledge you need for your
MB is knowledge of yourself ;-)

Cheers,

Conrad