Guys, I searched the archives, and I'm still confused.
How exactly do I get the engine codes from the diagnostic connector on my '91 300SE?

The connector is behind the battery, and has a big push-button next to it.
However, I see no LED.

I assume I need to rig a LED and connect a couple of the terminals, then push the button for 2-4 seconds, or ground something, or what?

Sorry to be so dumb, but I learned not to poke wires in expensive computers without 100% knowledge.

Any help is appreciated. I wandered thru the various posts, and found the blink harness, the code list, grounding termnal 3, etc;
but nothing exactly pertaining to a terminal that has a button and no LED.

Tks.