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Old 03-09-2003, 08:37 AM
KenP's Avatar
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Join Date: Dec 2002
Location: Southern New Hampshire
Posts: 418
Diagnostic Connector Differences?

Have had my 1996 S500 Coupe for only a few months, and am slowly starting to understand some of the complex engine/subsystem management schemes used by Mercedes... emphasis on the word "slowly". :-)
Anyway, have done some archive searches on this topic, but haven't found the answer... maybe somebody with experience on the on-board diagnostic systems can shed some light.
My car has both the OBD-II connector under the dash, and the "38 pin" connector under the hood. Took me a bit to find the 38 pin connector as its not in the module box... it is by itself near the coolant tank on the right inner fender.
Can someone give me an idea of what systems are accessible via the 38 pin connector that are not available via the ODB-II?
I have an excellent ODB-II readout system that runs on my laptop and have had no problem accessing many of the engine management functions via this port. I think that transmission trouble codes are also available via this port.
I understand the 38 pin connector is a digital only data port... and that "homemade" pulse counters won't work on my car.
Digital data readers for the 38 pin port are awfully expensive and am wondering what they add to the diagnostic puzzle?
I suspect that the ODB-II port only reveals those systems mandated by Federal law for emissions control and that Mercedes puts everything else into their own diagnostic system so I really need both readers.
Is that right?
Thanks, KenP
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Old 03-09-2003, 12:41 PM
JimF's Avatar
'94 S500: only 793 sold!
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,925
Here's some answers. . . .

what systems are available on the 38pin Diag Connector
Check MENU #2 showing a picture of the 38-pin connector. In the table below all of the available systems are shown for your car.

Regarding a scanner vs computer+sw: The only real advantage is the portability and compactness of the hand-held scanner vs the laptop plus adapter and sw.

The code readout is somewhat different in the OBD than what you read from the 38 pin connector with a "Mercedes" only scanner such as AST's Retreiver scanner. But a DTC is a DTC!!
Regards . . . . JimF
'94 S500 Cpe

Visit my Mercedes Web Page
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Old 03-10-2003, 03:09 PM
DR.DIESEL's Avatar
Senior Member
Join Date: Mar 2003
Location: Puget Sound, Washington St.
Posts: 522
The 38pin connector gives us diagnostic access to systems like airbag, pnuematic systems, inst cluster, remote locking and drive auth., headlamp range adj., climate control and so on.
The OBDII under the dash will provided standardized OBD codes that are required by the Fed gov. (Engine, tranny)
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