I was able to pull the codes just now and came out with:

#5 - Oxygen sensor (I unplugged it while the engine was running)

#9 - EHA (also unplugged while engine was running)

#10 Throttle position switch - closed throttle position switch fault (idle)

I am going to clear all codes and see if my CE light goes off, that would indicate that the components in question are ok, and the reason the CE light is on, is because of disconnecting while running, correct? The CE light wasn't on before...

Whats the deal with fault code #10?

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'89 300E - 153k miles - California car - Black/Palomino

Cleared the codes and nothing came back after 10 minutes of idling, I'm sure that isn't a true test but like I said, the CE light only came on because I unplugged stuff while running. Also, the led went completely off after all the codes were cleared.

How do you put the car in 'diagnostic mode' to get duty cycle at pins 3 & 2 of the X11 connector?

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'89 300E - 153k miles - California car - Black/Palomino

Got around to putting the car into 'diagnostic mode' and got an average of .99 +/- .003 at pin 3 of the X11 terminal. I don't know, but that seems extremely low, right?

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'89 300E - 153k miles - California car - Black/Palomino