Back on the subject of the computer, I just got off the phone with Bob at Beckmann Technologies Inc (800-742-1021), a company that repairs and sells Mercedes engine computers (even the new ones, and at a considerable discount.) During our conversation the subject of O2 sensors came up and I mentioned that one of my post-cat sensors appeared to be the wrong one (too long of a lead) but that my IT said it was no problem.

Bob informed me that it actually is a problem as the ME ECU cars must have the correct O2 sensors installed, if not the one wrong one (something different in how it grounds and the reference voltage) will "take down" all the others and indicate a circuit malfunction on all four. He stated that he has seen this problem more than a few times on ME ECU vehicles.

He recommended unplugging the wrong one and resetting the system with the OBDII device, which I will do first thing when I get home tonight. Hopefully this will result in only one (1) O2 circuit malfunction code, not four (4) as is now indicated.

Also plan to do much finger-crossing, praying, etc.

Bob at Beckmann also said that it is a known "fix" (NOT) for people to adapt the wiring to the ME ECU so that power comes from a switched circuit not a continuous one. That way, when the car is shut off, power to the ECU is also disconnected, erasing history and resetting the cycle counter. This is to prevent the check engine light from coming on, in order to pass emissions. This may be what was done (at one time, now reversed) under the plug cover on my car, but I will have to research the wiring diagram to make sure.