Embarassed to ask...
 

I just picked up a 1995 E420SE (W124) and I can't find the diagnostic connector. I've searched and I think it's supposed to be on the passenger side of the engine compartment but I don't see it. Does it have a cover or something on it that is not obvious to me.

I know it's a dumb question. Sorry it's my first W124.

Here's a picture of where I think it is...
 

I hope it's not too obvious :)

There are actually two - one is under the round cap on the piece that says "battery in trunk" and the other is the small rectangle just forward of the word "trunk"

I am a fool for w124s. Could I trouble you to post pictures of your latest gem?

Here she is...

And, 95 was a transition year towards OBD 2 so there might be a connector above the gas pedal ( maybe under a flip cover )

I just checked but not such luck. OBD2 would have been nice to help figure out the rough running issues I have.

There's no such thing as an E420SE.. It's an E420.

No Mercedes had OBD2 capability until 1997. There is a diagnostic port near the battery. You will need to build the diagnostic tool (research w124 diagnostic tool build) and there's a lot of threads on there.

Your rough running issues could be a number of thing.

I need you to answer a question for me. Has the wiring harnesses ever been replaced (upper and lower harness). If you don't have any prior knowledge of this being replaced, I suggest you check the date on the harnesses. Anything pre 1998 harnesses are biodegradable harnesses which cause running issues.

The wiring harness tag where the battery would be is dated 1994.
I did some pretty aggressive poking on the injector wires and the harness is bad.

What would be the part numbers for the upper and lower harness? Might as well do both while I'm there.

This kind of a little bit resembles the diagnostic port..maybe. Does the cover come off?

I know little of the 94+ 124s

http://i.imgur.com/HGPBVbV.jpg

Jake, I believe any car registered in the us from 96 up has to have the OBD2 connection. It is required for inspections. I don't know about Mercedes, but some cars had it in 1995.

PaulM

CAN I HAVE THAT DRIVER SEAT?
Just kidding....

Amen to...
 

... V8's. Nice car.

that round connector on the box where it says battery in trunk is where the diagnostic connector is. You won't be able to read it with any scan tool, you're gonna need the SDS to hook that up. This is a 124.034

That is a beauty - thanks for posting the picutres. MB really stuffed that engine into that engine bay, non?