Just when I thought this was all making sense, now I get thrown a curve. My 1990 300te has a 103.983 engine according to all documentation that I have ever seen. While trying to troubleshoot the duty cycle issue for a California car, I see that I have parts that are specified for a 104 engine.

Case in point; the pushbutton LED for diagnosis for a CA car as of 1988, an 8-pin version, is replaced by a 16-pin version on engines 104, 119. I have the 16-pin version.

Case in point; the KE Control Unit (N3) has a 25-pin configuration that is specified for engines 102, 103, 116, 117. I have the 55-pin version that is specified for engines 104, 119.

The reason that I have not been able to get my LED into the "continuous on" mode is because you can't do so with the 55-pin connector. It has a separate wire to contact 30 that supplies the on/off ratio (lambda test signal).

My duty cycle reading was 35% (rich). All of the write-ups I have seen say a CCW turn is needed to lean the fuel ratio back up to a target of 45%. When I tried to turn CCW, the ratio went lower and lower. I was able to get my ratio corrected to 45% by turning the tower screw CW by about 5 degrees from its' original position.

I have very few pages of wiring diagrams and test procedures from my WIS that apply to fuel management for this type of configuration. Do I need to now start looking at specs for 104 engines to figure out how to properly tune my car? When did MB start indroducing 104 components into the 103 engines? Is this just a California thing?