Here is a starting point for reading and understanding DTCs.
A friend in Belgium with a very close friend in Stuttgart has confirmed that story about the wiring harnesses on any 94-96 Benz. They made them with a new material that would break down in a biodegradeable form after their useful life was over. They must have forgotten the engine heat test when they were designing this harness. (No wonder these krauts lost the war;^)
Almost every harness is just about guaranteed to self-destruct. MB will officially tell you that that is bunk. Your local mechanic will pull out the harness and show you that it is not.
To eliminate the harness, you need to borrow one from a friend with another E500, E400 SL500 or any 119 engine. (The harness is the same even if the part number is different) Install the harness on a cold engine. Take the car out and duplicate the conditions that sent it into limp mode. If it does not repeat, you are lucky - it is definately the harness. If you threaten and cajole the dealer to connect you with an MBNA rep, he will do so and the rep will most certainly give you a new harness assuming you employ the use of Irish Diplomacy on him. It can be removed and re-installed in minutes so I would not offer the dealer a dime to do it.
If the ASR light does engage and send you into limp mode - it is most likely the air flow meter (potentiometer). The parts suppliers will not sell you that part unless you are an official re-builder of MB parts.
The entire unit is for sale here at $587.00 ish. There are four bolts and a gasket and the air cleaner housing seperating you from completing your task.
If you are handy with a wrench, some gasket cement and common sense - you can do the job yourself. If Guido's gang does it for you, plan on paying $7-900 bucks for the part and about an hour and a half pluck and chuck time to install it.