I've been trying to address my O2 sensor error on my 1990 190e 2.6. I'm getting a constant 50% duty cycle and 22 LED flashes, which indicates a problem w/ the heating circuit. My CD manual is telling me to test the signal from the O2 sensor to the CIS-E control unit, jack 8, and pull off the fuel pump relay and bridge jacks 7 and 8 and test for voltage.

My problems are these:
1) the plug to my CIS control unit is different than the one shown in the manual (which I believe shows the 1987 model); jack 8 has no contacts in it.
2) I have a MAS relay, not a fuel pump relay.

Does anyone have diagrams for the 1990 plug into the CIS control unit and/or the MAS relay? Any input appreciated.

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1990 190e 2.6 - The only one I can really call "My Car".

1987 190e 2.3 - The donor car's up and running, only mods are Euros and a Sony headunit. My Dad's runabout now.

1990 300e 2.6 - The parents' ride.